docs: def MultiNotifyQueue(self, notifications, mutation_pool=None):
      """This is the same as NotifyQueue but for several session_ids at once.
  
      Args:
        notifications: A list of notifications.
        mutation_pool: A MutationPool object to schedule Notifications on.
  
      Raises:
        RuntimeError: An invalid session_id was passed.
      """
      extract_queue = lambda notification: notification.session_id.Queue()
      for queue, notifications in iteritems(
          collection.Group(notifications, extract_queue)):
        self._MultiNotifyQueue(queue, notifications, mutation_pool=mutation_pool)