code: func (d *Data) Close() error {
  	if d.dh == nil {
  		return nil
  	}
  	if d.cbc > 0 {
  		callbackDelete(d.cbc)
  	}
  	_, err := C.gpgme_data_release(d.dh)
  	d.dh = nil
  	return err
  }
docs: // Close releases any resources associated with the data buffer