module.say_hi("FastAPI")

    mock_print.assert_called_once_with("Hey FastAPI!")

    with pytest.raises(
        TypeError,
        match=re.escape("say_hi() missing 1 required positional argument: 'name'"),
    ):

with `Annotated` would **not be affected** at all.

If you call those functions in **other places in your code**, the actual **default values** will be kept, your editor will help you notice missing **required arguments**, Python will require you to pass required arguments at **runtime**, you will be able to **use the same functions** for different things and with different libraries (e.g. **Typer** will soon support `Annotated` too, then you could use the same function for an API and a CLI),...

        return uuid.UUID

    @property
    def __dict__(self):
        """Spoof a missing __dict__ by raising TypeError, this is how
        asyncpg.pgroto.pgproto.UUID behaves"""
        raise TypeError("vars() argument must have __dict__ attribute")


def test_pydanticv2():
    from pydantic import field_serializer

    app = FastAPI()

    @app.get("/fast_uuid")
    def return_fast_uuid():