"ServerSentEvent. Use 'data' for JSON-serialized payloads "
                "or 'raw_data' for pre-formatted strings."
            )
        return self


def format_sse_event(
    *,
    data_str: Annotated[
        str | None,
        Doc(
            """
            Pre-serialized data string to use as the `data:` field.
            """
        ),
    ] = None,