Class Foo

tests/test_forward_ref.py:54–55

        from pydantic import BaseModel, PydanticUserError

        class Foo(BaseModel):
            a: Optional['Bar'] = None

        with pytest.raises(PydanticUserError, match='`Foo` is not fully defined; you should define `Bar`,'):
            Foo(a={'b': {'a': {}}})