docs: def _MultiNotifyQueue(self, queue, notifications, mutation_pool=None):
      """Does the actual queuing."""
      notification_list = []
      now = rdfvalue.RDFDatetime.Now()
      for notification in notifications:
        if not notification.first_queued:
          notification.first_queued = (
              self.frozen_timestamp or rdfvalue.RDFDatetime.Now())
        else:
          diff = now - notification.first_queued
          if diff.seconds >= self.notification_expiry_time:
            # This notification has been around for too long, we drop it.
            logging.debug("Dropping notification: %s", str(notification))
            continue
  
        notification_list.append(notification)
  
      mutation_pool.CreateNotifications(
          self.GetNotificationShard(queue), notification_list)