code: func (sp *Subscribe) String() string {
  	var subscriptions []string
  
  	for _, t := range sp.Subscriptions {
  		subscriptions = append(subscriptions, t.String())
  	}
  
  	return fmt.Sprintf("<Subscribe ID=%d Subscriptions=[%s]>",
  		sp.ID, strings.Join(subscriptions, ", "))
  }
docs: // String returns a string representation of the packet.