fix: Fix type parameters loading

Author: pawamoy

src/griffe/_internal/encoders.py

@@ -212,7 +212,7 @@ def _load_class(obj_dict: dict[str, Any]) -> Class:
         endlineno=obj_dict.get("endlineno"),
         docstring=_load_docstring(obj_dict),
         decorators=_load_decorators(obj_dict),
-        type_parameters=TypeParameters(*obj_dict["type_parameters"]),
+        type_parameters=TypeParameters(*obj_dict["type_parameters"]) if "type_parameters" in obj_dict else None,
         bases=obj_dict["bases"],
         runtime=obj_dict.get("runtime", True),
     )
@@ -239,7 +239,7 @@ def _load_function(obj_dict: dict[str, Any]) -> Function:
         parameters=Parameters(*obj_dict["parameters"]),
         returns=obj_dict["returns"],
         decorators=_load_decorators(obj_dict),
-        type_parameters=TypeParameters(*obj_dict["type_parameters"]),
+        type_parameters=TypeParameters(*obj_dict["type_parameters"]) if "type_parameters" in obj_dict else None,
         lineno=obj_dict["lineno"],
         endlineno=obj_dict.get("endlineno"),
         docstring=_load_docstring(obj_dict),

src/griffe/_internal/models.py

@@ -614,6 +614,9 @@ def __init__(
         [`has_docstrings`][griffe.Object.has_docstrings].
         """
 
+        # TODO: Maybe move these into `Class` and `Function`.
+        # Then always return them in `Class` and `Function`'s `as_dict` methods,
+        # and remove the conditional in the `_load_class` and `_load_function` decoders.
         self.type_parameters: TypeParameters = type_parameters or TypeParameters()
         """The object type parameters."""