code: def action_type(self):
          
          if self.start_message:
              return self.start_message.contents[ACTION_TYPE_FIELD]
          elif self.end_message:
              return self.end_message.contents[ACTION_TYPE_FIELD]
          else:
              return None
docs: The type of this action, e.g. C{"yourapp:subsystem:dosomething"}.