code: def _receive_callback(self, raw_message):
          
          message = self.backend.message_to_python(raw_message)
          if self.auto_ack and not message.acknowledged:
              message.ack()
          try:
              decoded = message.decode()
          except Exception, exc:
              if not self.on_decode_error:
                  raise
              self.on_decode_error(message, exc)
          else:
              self.receive(decoded, message)
docs: Internal method used when a message is received in consume mode.