Start queueing the chain to the worker cluster
        :return: the chain's group id

def run(self):
        """
        Start queueing the chain to the worker cluster
        :return: the chain's group id
        """
        self.group = async_chain(chain=self.chain[:], group=self.group, cached=self.cached, sync=self.sync,
                                 broker=self.broker)
        self.started = True
        return self.group