code: def GetFormatStringAttributeNames(self, event):
      
      event_formatter = self.GetEventFormatter(event)
      if not event_formatter:
        return None
  
      return event_formatter.GetFormatStringAttributeNames()
docs: Retrieves the attribute names in the format string.
  
      Args:
        event (EventObject): event.
  
      Returns:
        list[str]: list containing the attribute names. If no event formatter to
            match the event can be found the function returns None.