Called when the client is listening, and somebody marks a message as seen

        :param seen_by: The ID of the person who marked the message as seen
        :param thread_id: Thread ID that the action was sent to. See :ref:`intro_threads`
        :param thread_type: Type of thread that the action was sent to. See :ref:`intro_threads`
        :param seen_ts: A timestamp of when the person saw the message
        :param ts: A timestamp of the action
        :param metadata: Extra metadata about the action
        :param msg: A full set of the data recieved
        :type thread_type: models.ThreadType

def onMessageSeen(
        self,
        seen_by=None,
        thread_id=None,
        thread_type=ThreadType.USER,
        seen_ts=None,
        ts=None,
        metadata=None,
        msg=None,
    ):
        """
        Called when the client is listening, and somebody marks a message as seen

        :param seen_by: The ID of the person who marked the message as seen
        :param thread_id: Thread ID that the action was sent to. See :ref:`intro_threads`
        :param thread_type: Type of thread that the action was sent to. See :ref:`intro_threads`
        :param seen_ts: A timestamp of when the person saw the message
        :param ts: A timestamp of the action
        :param metadata: Extra metadata about the action
        :param msg: A full set of the data recieved
        :type thread_type: models.ThreadType
        """
        log.info(
            "Messages seen by {} in {} ({}) at {}s".format(
                seen_by, thread_id, thread_type.name, seen_ts / 1000
            )
        )