code: func (v *Notebook) GetActionWidget(packType PackType) (*Widget, error) {
  	c := C.gtk_notebook_get_action_widget(v.native(),
  		C.GtkPackType(packType))
  	if c == nil {
  		return nil, nilPtrErr
  	}
  	return wrapWidget(glib.Take(unsafe.Pointer(c))), nil
  }
docs: // GetActionWidget() is a wrapper around gtk_notebook_get_action_widget().