def METHOD_NAME(
    self, message: "gapic_types.PubsubMessage"
) -> Optional["pubsub_v1.publisher.futures.Future"]:  # pragma: NO COVER
    """Publish a single message.
    Add the given message to this object; this will cause it to be
    published once the batch either has enough messages or a sufficient
    period of time has elapsed.
    This method is called by :meth:`~.PublisherClient.publish`.
    Args:
        message: The Pub/Sub message.
    Returns:
        An object conforming to the :class:`concurrent.futures.Future` interface.
        If :data:`None` is returned, that signals that the batch cannot
        accept a message.
    """
    raise NotImplementedError