This method removes one actor from the Host, stoping it and deleting
        all its references.

        :param str. aid: identifier of the actor you want to stop.

def stop_actor(self, aid):
        '''
        This method removes one actor from the Host, stoping it and deleting
        all its references.

        :param str. aid: identifier of the actor you want to stop.
        '''
        url = '%s://%s/%s' % (self.transport, self.host_url.netloc, aid)
        if url != self.url:
            actor = self.actors[url]
            Proxy(actor).stop()
            actor.thread.join()
            del self.actors[url]
            del self.threads[actor.thread]