code: def ack(self, tup_id):
          
          self.failed_tuples.pop(tup_id, None)
          try:
              del self.unacked_tuples[tup_id]
          except KeyError:
              self.logger.error("Received ack for unknown tuple ID: %r", tup_id)
docs: Called when a bolt acknowledges a Tuple in the topology.
  
          :param tup_id: the ID of the Tuple that has been fully acknowledged in
                         the topology.
          :type tup_id: str