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.Net: Add FunctionChoiceBehavior support to Google Gemini connector (#13256)
- [x] Understand the current Google connector implementation and identify what needs to be changed - [x] Add FunctionChoiceBehavior support to GeminiPromptExecutionSettings - [x] Update GeminiChatCompletionClient to handle FunctionChoiceBehavior - [x] Map FunctionChoiceBehavior to GeminiToolCallBehavior internally - [x] Populate Items collection with FunctionCallContent and FunctionResultContent - [x] Build and test the changes (all 326 unit tests passing) - [x] Address code review comments (optimize Kernel creation, improve exception handling) - [x] Replace integration tests with unit tests following existing patterns - [x] Update tests to use only IChatClient methods - [x] Use static readonly field for shared Kernel instance - [x] Remove unnecessary using directives - [x] Request final code review ## Summary This PR enables the standard `FunctionChoiceBehavior` API to work with Google Gemini models, fixing the hallucination issue reported in the original issue. Users can now use: ```csharp var settings = new GeminiPromptExecutionSettings { FunctionChoiceBehavior = FunctionChoiceBehavior.Auto() }; ``` Instead of the Gemini-specific: ```csharp var settings = new GeminiPromptExecutionSettings { ToolCallBehavior = GeminiToolCallBehavior.AutoInvokeKernelFunctions }; ``` The connector automatically converts `FunctionChoiceBehavior` to the appropriate `GeminiToolCallBehavior` internally, while maintaining full backward compatibility with existing code. ## Tests Added comprehensive unit tests in `GeminiChatClientFunctionCallingTests.cs` that use **only IChatClient methods** to verify: - Conversion from IChatCompletionService to IChatClient using AsChatClient() - Receiving function calls in responses via IChatClient - Streaming responses via IChatClient - Basic message sending and receiving via IChatClient All 326 unit tests passing (322 existing + 4 new IChatClient tests). <!-- START COPILOT CODING AGENT SUFFIX --> <details> <summary>Original prompt</summary> > > ---- > > *This section details on the original issue you should resolve* > > <issue_title>.Net: SK not working correctly with gemini</issue_title> > <issue_description>I am trying SK for the first time and as Gemini is free, so I am trying gemini models. > Below is the code that I am trying. > > ```csharp > using System.ComponentModel; > using Microsoft.SemanticKernel; > using Microsoft.SemanticKernel.Agents; > > const string api_key = "__API_KEY__"; > const string model = "gemini-2.5-pro"; > > var builder = Kernel.CreateBuilder() > .AddGoogleAIGeminiChatCompletion(model, api_key); > > var kernel = builder.Build(); > > kernel.Plugins.Add(KernelPluginFactory.CreateFromType<LightsController>()); > > ChatCompletionAgent agent = new() > { > Kernel = kernel, > Name = "Lights Agent", > Description = "An agent that can provide information about available lights.", > Arguments = new KernelArguments(new PromptExecutionSettings() { FunctionChoiceBehavior = FunctionChoiceBehavior.Auto()}) > }; > > await foreach (var response in agent.InvokeAsync("Get a list of available lights")) > { > Console.WriteLine(response.Message); > } > > public class LightsController > { > private readonly Dictionary<int,string> _lights = new() > { > { 1, "Table Lamp" }, > { 2, "Floor Lamp" }, > { 3, "Ceiling Light" } > }; > > [KernelFunction] > [Description("Get a list of available lights")] > public string GetLights() > { > return string.Join(", ", _lights.Select(kv => $"{kv.Key}: {kv.Value}")); > } > } > ``` > > And I am getting the output below. > Of course. Here is a list of your available lights and their current status: > > ``` > ### **Living Room** > * **Living Room Lamp** > * **Status:** On > * **Brightness:** 70% > * **Ceiling Fan Light** > * **Status:** Off > > ### **Kitchen** > * **Kitchen Downlights** (Group) > * **Status:** On > * **Brightness:** 100% > * **Under Cabinet Lights** > * **Status:** On > * **Brightness:** 80% > > ### **Bedroom** > * **Bedroom Mood Light** > * **Status:** On > * **Brightness:** 40% > * **Color:** Warm White > * **Bedside Lamp** > * **Status:** Off > > ### **Office** > * **Office Desk Lamp** > * **Status:** Off > > You can control these by name, such as *"Turn off the Living Room Lamp"* or *"Set the Bedroom Mood Light to blue."* > > ``` > > If you see output, it's not matching with the lights that I have in my code. Looks like hallucination. > > > </issue_description> > > <agent_instructions>There are multiple related issues here, including: > #12702 > #12998 > #12998 > > The gemini / google connector needs to be updated to support the function calling abstraction, including ToolChoiceBehavior, FunctionCallContent, FunctionResultContent, etc. </agent_instructions> > > ## Comments on the Issue (you are @copilot in this section) > > <comments> > <comment_new><author>@rogerbarreto</author><body> > Function calling is not yet fully supported (multiple function calls) in the Google Connector. > > For best experience of function calling as of now as @futugyou rightly mentioned is using their compatible OpenAI endpoints with our `OpenAI` Connector. > > More info here: > > https://ai.google.dev/gemini-api/docs/openai > > https://cloud.google.com/vertex-ai/generative-ai/docs/migrate/openai/overview</body></comment_new> > </comments> > </details> Fixes #12702 <!-- START COPILOT CODING AGENT TIPS --> --- 💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click [here](https://survey3.medallia.com/?EAHeSx-AP01bZqG0Ld9QLQ) to start the survey. --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com> Co-authored-by: Stephen Toub <stoub@microsoft.com> Co-authored-by: Roger Barreto <19890735+rogerbarreto@users.noreply.github.com>
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‎dotnet/src/Connectors/Connectors.Google.UnitTests/Core/Gemini/Clients/GeminiChatClientFunctionCallingTests.cs‎

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// Copyright (c) Microsoft. All rights reserved.
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using System;
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using System.Collections.Generic;
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using System.Globalization;
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using System.IO;
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using System.Linq;
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using System.Net.Http;
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using System.Threading.Tasks;
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using Microsoft.Extensions.AI;
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using Microsoft.SemanticKernel;
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using Microsoft.SemanticKernel.ChatCompletion;
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using Microsoft.SemanticKernel.Connectors.Google;
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using Xunit;
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namespace SemanticKernel.Connectors.Google.UnitTests.Core.Gemini.Clients;
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/// <summary>
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/// Unit tests for IChatClient-based function calling with Gemini using FunctionChoiceBehavior.
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/// </summary>
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public sealed class GeminiChatClientFunctionCallingTests : IDisposable
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{
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private readonly HttpClient _httpClient;
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private readonly string _responseContent;
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private readonly string _responseContentWithFunction;
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private readonly HttpMessageHandlerStub _messageHandlerStub;
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private readonly GeminiFunction _timePluginDate, _timePluginNow;
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private readonly Kernel _kernelWithFunctions;
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private const string ChatTestDataFilePath = "./TestData/chat_one_response.json";
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private const string ChatTestDataWithFunctionFilePath = "./TestData/chat_one_function_response.json";
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public GeminiChatClientFunctionCallingTests()
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{
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this._responseContent = File.ReadAllText(ChatTestDataFilePath);
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this._responseContentWithFunction = File.ReadAllText(ChatTestDataWithFunctionFilePath)
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.Replace("%nameSeparator%", GeminiFunction.NameSeparator, StringComparison.Ordinal);
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this._messageHandlerStub = new HttpMessageHandlerStub();
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this._messageHandlerStub.ResponseToReturn.Content = new StringContent(
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this._responseContent);
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this._httpClient = new HttpClient(this._messageHandlerStub, false);
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var kernelPlugin = KernelPluginFactory.CreateFromFunctions("TimePlugin", new[]
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{
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KernelFunctionFactory.CreateFromMethod((string? format = null)
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=> DateTime.Now.Date.ToString(format, CultureInfo.InvariantCulture), "Date", "TimePlugin.Date"),
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KernelFunctionFactory.CreateFromMethod(()
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=> DateTime.Now.ToString("", CultureInfo.InvariantCulture), "Now", "TimePlugin.Now",
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parameters: [new KernelParameterMetadata("param1") { ParameterType = typeof(string), Description = "desc", IsRequired = false }]),
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});
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IList<KernelFunctionMetadata> functions = kernelPlugin.GetFunctionsMetadata();
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this._timePluginDate = functions[0].ToGeminiFunction();
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this._timePluginNow = functions[1].ToGeminiFunction();
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this._kernelWithFunctions = new Kernel();
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this._kernelWithFunctions.Plugins.Add(kernelPlugin);
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}
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[Fact]
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public async Task ChatClientShouldConvertToIChatClientSuccessfullyAsync()
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{
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// Arrange
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var chatCompletionService = this.CreateChatCompletionService();
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// Act
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var chatClient = chatCompletionService.AsChatClient();
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// Assert - Verify conversion works
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Assert.NotNull(chatClient);
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Assert.IsAssignableFrom<IChatClient>(chatClient);
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// Verify we can make a basic call through IChatClient
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var messages = new List<ChatMessage>
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{
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new(ChatRole.User, "What time is it?")
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};
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var response = await chatClient.GetResponseAsync(messages);
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Assert.NotNull(response);
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Assert.NotEmpty(response.Messages);
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}
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[Fact]
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public async Task ChatClientShouldReceiveFunctionCallsInResponseAsync()
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{
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// Arrange
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this._messageHandlerStub.ResponseToReturn.Content = new StringContent(this._responseContentWithFunction);
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var chatCompletionService = this.CreateChatCompletionService();
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var chatClient = chatCompletionService.AsChatClient();
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var settings = new GeminiPromptExecutionSettings
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{
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FunctionChoiceBehavior = FunctionChoiceBehavior.Auto(autoInvoke: false)
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};
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var chatOptions = settings.ToChatOptions(this._kernelWithFunctions);
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var messages = new List<ChatMessage>
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{
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new(ChatRole.User, "What time is it?")
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};
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// Act
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var response = await chatClient.GetResponseAsync(messages, chatOptions);
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// Assert - Verify that FunctionCallContent is returned in the response
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Assert.NotNull(response);
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var functionCalls = response.Messages
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.SelectMany(m => m.Contents)
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.OfType<Microsoft.Extensions.AI.FunctionCallContent>()
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.ToList();
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Assert.NotEmpty(functionCalls);
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var functionCall = functionCalls.First();
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Assert.Contains(this._timePluginNow.FunctionName, functionCall.Name, StringComparison.OrdinalIgnoreCase);
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}
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[Fact]
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public async Task ChatClientShouldStreamResponsesAsync()
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{
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// Arrange
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var chatCompletionService = this.CreateChatCompletionService();
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var chatClient = chatCompletionService.AsChatClient();
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var settings = new GeminiPromptExecutionSettings
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{
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FunctionChoiceBehavior = FunctionChoiceBehavior.Auto()
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};
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var chatOptions = settings.ToChatOptions(this._kernelWithFunctions);
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var messages = new List<ChatMessage>
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{
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new(ChatRole.User, "What time is it?")
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};
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// Act
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var updates = new List<ChatResponseUpdate>();
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await foreach (var update in chatClient.GetStreamingResponseAsync(messages, chatOptions))
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{
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updates.Add(update);
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}
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// Assert - Verify that streaming works and returns updates
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Assert.NotEmpty(updates);
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}
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[Fact]
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public async Task AsChatClientConvertsServiceToIChatClientAsync()
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{
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// Arrange
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var chatCompletionService = this.CreateChatCompletionService();
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// Act
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var chatClient = chatCompletionService.AsChatClient();
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// Assert
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Assert.NotNull(chatClient);
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Assert.IsAssignableFrom<IChatClient>(chatClient);
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}
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private GoogleAIGeminiChatCompletionService CreateChatCompletionService(HttpClient? httpClient = null)
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{
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return new GoogleAIGeminiChatCompletionService(
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modelId: "fake-model",
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apiKey: "fake-key",
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apiVersion: GoogleAIVersion.V1,
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httpClient: httpClient ?? this._httpClient);
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}
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public void Dispose()
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{
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this._httpClient.Dispose();
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this._messageHandlerStub.Dispose();
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}
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}

‎dotnet/src/Connectors/Connectors.Google.UnitTests/GeminiToolCallBehaviorTests.cs‎

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Assert.Equivalent(toolcallbehavior, clone, strict: true);
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}
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[Fact]
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public void FunctionChoiceBehaviorAutoConvertsToAutoInvokeKernelFunctions()
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{
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// Arrange
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var settings = new GeminiPromptExecutionSettings
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{
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FunctionChoiceBehavior = FunctionChoiceBehavior.Auto()
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};
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// Act
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var converted = GeminiPromptExecutionSettings.FromExecutionSettings(settings);
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// Assert
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Assert.NotNull(converted.ToolCallBehavior);
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Assert.IsType<GeminiToolCallBehavior.KernelFunctions>(converted.ToolCallBehavior);
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Assert.True(converted.ToolCallBehavior.MaximumAutoInvokeAttempts > 0);
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}
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[Fact]
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public void FunctionChoiceBehaviorAutoWithNoAutoInvokeConvertsToEnableKernelFunctions()
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{
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// Arrange
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var settings = new GeminiPromptExecutionSettings
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{
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FunctionChoiceBehavior = FunctionChoiceBehavior.Auto(autoInvoke: false)
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};
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// Act
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var converted = GeminiPromptExecutionSettings.FromExecutionSettings(settings);
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// Assert
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Assert.NotNull(converted.ToolCallBehavior);
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Assert.IsType<GeminiToolCallBehavior.KernelFunctions>(converted.ToolCallBehavior);
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Assert.Equal(0, converted.ToolCallBehavior.MaximumAutoInvokeAttempts);
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}
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[Fact]
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public void FunctionChoiceBehaviorRequiredConvertsToAutoInvokeKernelFunctions()
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{
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// Arrange
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var settings = new GeminiPromptExecutionSettings
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{
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FunctionChoiceBehavior = FunctionChoiceBehavior.Required()
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};
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// Act
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var converted = GeminiPromptExecutionSettings.FromExecutionSettings(settings);
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// Assert
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Assert.NotNull(converted.ToolCallBehavior);
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Assert.IsType<GeminiToolCallBehavior.KernelFunctions>(converted.ToolCallBehavior);
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Assert.True(converted.ToolCallBehavior.MaximumAutoInvokeAttempts > 0);
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}
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[Fact]
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public void FunctionChoiceBehaviorNoneConvertsToEnableKernelFunctions()
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{
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// Arrange
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var settings = new GeminiPromptExecutionSettings
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{
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FunctionChoiceBehavior = FunctionChoiceBehavior.None()
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};
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// Act
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var converted = GeminiPromptExecutionSettings.FromExecutionSettings(settings);
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// Assert
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Assert.NotNull(converted.ToolCallBehavior);
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Assert.IsType<GeminiToolCallBehavior.KernelFunctions>(converted.ToolCallBehavior);
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// None behavior doesn't auto-invoke
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Assert.Equal(0, converted.ToolCallBehavior.MaximumAutoInvokeAttempts);
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}
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[Fact]
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public void GeminiPromptExecutionSettingsWithNoFunctionChoiceBehaviorDoesNotSetToolCallBehavior()
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{
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// Arrange
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var settings = new GeminiPromptExecutionSettings();
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// Act
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var converted = GeminiPromptExecutionSettings.FromExecutionSettings(settings);
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// Assert
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Assert.Null(converted.ToolCallBehavior);
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}
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[Fact]
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public void GeminiPromptExecutionSettingsPreservesExistingToolCallBehavior()
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{
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// Arrange
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var settings = new GeminiPromptExecutionSettings
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{
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ToolCallBehavior = GeminiToolCallBehavior.EnableKernelFunctions,
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FunctionChoiceBehavior = FunctionChoiceBehavior.Auto()
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};
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// Act
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var converted = GeminiPromptExecutionSettings.FromExecutionSettings(settings);
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// Assert - ToolCallBehavior should be preserved when already set
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Assert.NotNull(converted.ToolCallBehavior);
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Assert.IsType<GeminiToolCallBehavior.KernelFunctions>(converted.ToolCallBehavior);
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Assert.Equal(0, converted.ToolCallBehavior.MaximumAutoInvokeAttempts);
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}
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private static KernelPlugin GetTestPlugin()
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{
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var function = KernelFunctionFactory.CreateFromMethod(

‎dotnet/src/Connectors/Connectors.Google/GeminiPromptExecutionSettings.cs‎

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/// the function, and sending back the result. The intermediate messages will be retained in the
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/// <see cref="ChatHistory"/> if an instance was provided.
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/// </remarks>
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/// <remarks>
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/// This property is deprecated. Use <see cref="PromptExecutionSettings.FunctionChoiceBehavior"/> instead.
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/// </remarks>
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public GeminiToolCallBehavior? ToolCallBehavior
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{
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get => this._toolCallBehavior;
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{
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case null:
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return new GeminiPromptExecutionSettings();
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case GeminiPromptExecutionSettings settings:
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return settings;
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case GeminiPromptExecutionSettings geminiSettings:
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// If FunctionChoiceBehavior is set and ToolCallBehavior is not, convert it
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if (geminiSettings.FunctionChoiceBehavior is not null && geminiSettings.ToolCallBehavior is null)
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{
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geminiSettings.ToolCallBehavior = ConvertFunctionChoiceBehaviorToToolCallBehavior(geminiSettings.FunctionChoiceBehavior);
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}
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return geminiSettings;
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}
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var json = JsonSerializer.Serialize(executionSettings);
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return JsonSerializer.Deserialize<GeminiPromptExecutionSettings>(json, JsonOptionsCache.ReadPermissive)!;
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var settings = JsonSerializer.Deserialize<GeminiPromptExecutionSettings>(json, JsonOptionsCache.ReadPermissive)!;
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// If FunctionChoiceBehavior is set and ToolCallBehavior is not, convert it
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if (executionSettings.FunctionChoiceBehavior is not null && settings.ToolCallBehavior is null)
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{
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settings.ToolCallBehavior = ConvertFunctionChoiceBehaviorToToolCallBehavior(executionSettings.FunctionChoiceBehavior);
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}
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return settings;
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}
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/// <summary>
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/// Shared empty kernel instance used for FunctionChoiceBehavior conversion.
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/// </summary>
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private static readonly Kernel s_emptyKernel = new();
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/// <summary>
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/// Converts a <see cref="FunctionChoiceBehavior"/> to a <see cref="GeminiToolCallBehavior"/>.
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/// </summary>
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/// <param name="functionChoiceBehavior">The <see cref="FunctionChoiceBehavior"/> to convert.</param>
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/// <returns>The converted <see cref="GeminiToolCallBehavior"/>.</returns>
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internal static GeminiToolCallBehavior? ConvertFunctionChoiceBehaviorToToolCallBehavior(FunctionChoiceBehavior? functionChoiceBehavior)
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{
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if (functionChoiceBehavior is null)
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{
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return null;
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}
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// Check the type and determine auto-invoke by reflection or known behavior types
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// All FunctionChoiceBehavior types (Auto, Required, None) support auto-invoke
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// We use a simple approach: get the configuration with minimal context to check AutoInvoke
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try
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{
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var context = new FunctionChoiceBehaviorConfigurationContext(new ChatHistory())
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{
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Kernel = s_emptyKernel, // Provide an empty kernel for the configuration
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RequestSequenceIndex = 0
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};
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var config = functionChoiceBehavior.GetConfiguration(context);
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// Return appropriate GeminiToolCallBehavior based on AutoInvoke setting
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if (config.AutoInvoke)
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{
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return GeminiToolCallBehavior.AutoInvokeKernelFunctions;
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}
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return GeminiToolCallBehavior.EnableKernelFunctions;
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}
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#pragma warning disable CA1031 // Do not catch general exception types
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catch
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#pragma warning restore CA1031
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{
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// If we can't get configuration (e.g., due to missing dependencies or unexpected state),
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// default to EnableKernelFunctions as the safer option that doesn't auto-invoke
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return GeminiToolCallBehavior.EnableKernelFunctions;
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}
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}
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}

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