code: func (s *Subscription) Pending() (int, int, error) {
  	if s == nil {
  		return -1, -1, ErrBadSubscription
  	}
  	s.mu.Lock()
  	defer s.mu.Unlock()
  	if s.conn == nil {
  		return -1, -1, ErrBadSubscription
  	}
  	if s.typ == ChanSubscription {
  		return -1, -1, ErrTypeSubscription
  	}
  	return s.pMsgs, s.pBytes, nil
  }
docs: // Pending returns the number of queued messages and queued bytes in the client for this subscription.