code: func (r *RelayMessageOption) SetRelayMessage(p *RelayMessage) error {
  	b, err := p.MarshalBinary()
  	if err != nil {
  		return err
  	}
  
  	*r = b
  	return nil
  }
docs: // SetRelayMessage sets a RelayMessage (e.g. Relay Forward, Relay Reply) into this option.