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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def GetEventTagByIdentifier(self, identifier):
 """Retrieves a specific event tag. Args: identifier (SQLTableIdentifier):
 event tag identifier. Returns: EventTag: event tag or None if not available. """

    event_tag = self._GetAttributeContainerByIndex(
        self._CONTAINER_TYPE_EVENT_TAG, identifier.row_identifier - 1)
    if event_tag:
      event_identifier = identifiers.SQLTableIdentifier(
          self._CONTAINER_TYPE_EVENT, event_tag.event_row_identifier)
      event_tag.SetEventIdentifier(event_identifier)

      del event_tag.event_row_identifier

    return event_tag