def test_mutable_mapping_userdict_subclass() -> None:
    """Addresses https://github.com/pydantic/pydantic/issues/9549.

    Note - we still don't do a good job of handling subclasses, as we convert the input to a dict.
    """
    adapter = TypeAdapter(MutableMapping, config=ConfigDict(strict=True))

    assert isinstance(adapter.validate_python(UserDict()), MutableMapping)
Addresses https://github.com/pydantic/pydantic/issues/9549.

    Note - we still don't do a good job of handling subclasses, as we convert the input to a dict.
    
tests/test_types.py