Stop ZMQ tools.
        :return: self

def stop(self):
        """
        Stop ZMQ tools.
        :return: self
        """
        LOGGER.debug("zeromq.Driver.stop")
        for publisher in self.publishers_registry:
            publisher.stop()
        self.publishers_registry.clear()
        for subscriber in self.subscribers_registry:
            if subscriber.is_started:
                subscriber.stop()
        self.subscribers_registry.clear()
        # pykka.ActorRegistry.stop_all()
        return self