str,
        Doc(
            """
            The media type of this parameter field. Changing it would affect the
            generated OpenAPI, but currently it doesn't affect the parsing of the data.
            """
        ),
    ] = "application/json",
    alias: Annotated[
        Optional[str],
        Doc(
            """

    client = TestClient(app)
    with warnings.catch_warnings(record=True) as w:
        warnings.simplefilter("always")
        client.get("/openapi.json")
        assert len(w) >= 2
        duplicate_warnings = [
            warning for warning in w if issubclass(warning.category, UserWarning)
        ]
        assert len(duplicate_warnings) > 0