code: async def service(self, limit=None, quota: Optional[Quota] = None) -> int:
          
          if self.listener:
              await self._serviceStack(self.age, quota)
          else:
              logger.info("{} is stopped".format(self))
  
          r = len(self.rxMsgs)
          if r > 0:
              pracLimit = limit if limit else sys.maxsize
              return self.processReceived(pracLimit)
          return 0
docs: Service `limit` number of received messages in this stack.
  
          :param limit: the maximum number of messages to be processed. If None,
          processes all of the messages in rxMsgs.
          :return: the number of messages processed.