code: def ask(actor, message):
      
      sender = PromiseActorRef()
      actor.tell(message, sender)
      return sender.promise.future
docs: Send a message to `actor` and return a :class:`Future` holding a possible
      reply.
  
      To receive a result, the actor MUST send a reply to `sender`.
  
      :param actor:
      :type actor: :class:`ActorRef`.
  
      :param message:
      :type message: :type: Any
  
      :return: A future holding the result.