)
        value: Union[str, Missing] = Missing()
        embedded_model: EmbeddedModel = EmbeddedModel()

    @app.post("/")
    def foo(req: Model) -> dict[str, Union[str, None]]:
        return {
            "value": req.value or None,
            "embedded_value": req.embedded_model.value or None,
        }

    client = TestClient(app)

    response = client.post("/", json={})