code: def _MergeEventTag(self, storage_writer, attribute_container):
      if attribute_container.CONTAINER_TYPE != 'event_tag':
        return
      event_identifier = attribute_container.GetEventIdentifier()
      if not event_identifier:
        return
      stored_event_tag = self._event_tag_index.GetEventTagByIdentifier(
          storage_writer, event_identifier)
      if stored_event_tag:
        attribute_container.AddComment(stored_event_tag.comment)
        attribute_container.AddLabels(stored_event_tag.labels)
      self._event_tag_index.SetEventTag(attribute_container)