code: func (r *RelayMessageOption) RelayMessage() (*RelayMessage, error) {
  	rm := new(RelayMessage)
  	err := rm.UnmarshalBinary(*r)
  	if err != nil {
  		return nil, err
  	}
  
  	return rm, nil
  }
docs: // RelayMessage gets the relay message (e.g. Relay Forward, Relay Reply) into
  // this option (when hopcount > 0 of outer RelayMessage).