docs: def has_actor(self, aid):
          '''
          Checks if the given id is used in the host by some actor.
  
          :param str. aid: identifier of the actor to check.
          :return: True if the id is used within the host.
          '''
          url = '%s://%s/%s' % (self.transport, self.host_url.netloc, aid)
          return url in self.actors.keys()