def auto_unsubscribe(self, sid, limit=1):
        """
        Sends an UNSUB command to the server.  Unsubscribe is one of the basic building
        blocks in order to be able to define request/response semantics via pub/sub
        by announcing the server limited interest a priori.
        """
        if self.is_draining:
            raise ErrConnectionDraining
        yield self._unsubscribe(sid, limit)