encode_message

def encode_message(
    msg: Union[Sequence["SendableMessage"], "SendableMessage"],
) -> Tuple[bytes, Optional[str]]:
    """Encodes a message."""
    if msg is None:
        return (
            b"",
            None,
        )

    if isinstance(msg, bytes):
        return (
            msg,
            None,
        )

    if isinstance(msg, str):
        return (
            msg.encode(),
            ContentTypes.text.value,
        )

    return (
        dump_json(msg),
        ContentTypes.json.value,
    )