code: def _recv_ack(self, method_frame):
          '''Receive an ack from the broker.'''
          if self._ack_listener:
              delivery_tag = method_frame.args.read_longlong()
              multiple = method_frame.args.read_bit()
              if multiple:
                  while self._last_ack_id < delivery_tag:
                      self._last_ack_id += 1
                      self._ack_listener(self._last_ack_id)
              else:
                  self._last_ack_id = delivery_tag
                  self._ack_listener(self._last_ack_idf _recv_ack(self, method_frame):
          '''Receive an ack from the broker.'''
          if self._ack_listener:
              delivery_tag = method_frame.args.read_longlong()
              multiple = method_frame.args.read_bit()
              if multiple:
                  while self._last_ack_id < delivery_tag:
                      self._last_ack_id += 1
                      self._ack_listener(self._last_ack_id)
              else:
                  self._last_ack_id = delivery_tag
                  self._ack_listener(self._last_ack_id)
docs: Receive an ack from the broker.