code: func VolumeButtonNew() (*VolumeButton, error) {
  	c := C.gtk_volume_button_new()
  	if c == nil {
  		return nil, nilPtrErr
  	}
  	return wrapVolumeButton(glib.Take(unsafe.Pointer(c))), nil
  }
docs: // VolumeButtonNew() is a wrapper around gtk_button_new().