code: func (rm *retrieveManager) deliver(peer distPeer, msg *Msg) error {
  	rm.lock.RLock()
  	req, ok := rm.sentReqs[msg.ReqID]
  	rm.lock.RUnlock()
  
  	if ok {
  		return req.deliver(peer, msg)
  	}
  	return errResp(ErrUnexpectedResponse, "reqID = %v", msg.ReqID)
  }
docs: // deliver is called by the LES protocol manager to deliver reply messages to waiting requests