fix(dataset): preserve push_data compatibility with the released Apify SDK

src/crawlee/storage_clients/_base/_dataset_client.py

@@ -1,10 +1,11 @@
 from __future__ import annotations
 
 from abc import ABC, abstractmethod
+from collections.abc import Sequence
 from typing import TYPE_CHECKING
 
 if TYPE_CHECKING:
-    from collections.abc import AsyncIterator, Mapping, Sequence
+    from collections.abc import AsyncIterator, Mapping
 
     from crawlee._types import JsonSerializable
     from crawlee.storage_clients.models import DatasetItemsListPage, DatasetMetadata
@@ -91,3 +92,16 @@ async def iterate_items(
         raise NotImplementedError
         if False:
             yield {}
+
+    @staticmethod
+    def _is_sequence_of_items(
+        data: Sequence[Mapping[str, JsonSerializable]] | Mapping[str, JsonSerializable],
+    ) -> bool:
+        """Tell whether the `push_data` payload is a sequence of items rather than a single item.
+
+        No `push_data` implementation in this repository uses this helper - it is inlined there instead. It stays
+        on the base class because the Apify SDK up to 4.0.1 calls it from `ApifyDatasetClient.push_data`, so
+        removing it breaks every Actor that resolves such an SDK version against this package. Drop it in the
+        next major version, once those SDK versions are out of the supported range.
+        """
+        return isinstance(data, Sequence)