code: def receive(self, message_data, message):
          
          if not self.callbacks:
              raise NotImplementedError("No consumer callbacks registered")
          for callback in self.callbacks:
              callback(message_data, message)
docs: This method is called when a new message is received by
          running :meth:`wait`, :meth:`process_next` or :meth:`iterqueue`.
  
          When a message is received, it passes the message on to the
          callbacks listed in the :attr:`callbacks` attribute.
          You can register callbacks using :meth:`register_callback`.
  
          :param message_data: The deserialized message data.
  
          :param message: The :class:`carrot.backends.base.BaseMessage` instance.
  
          :raises NotImplementedError: If no callbacks has been registered.