code: func (v *Dialog) AddButton(text string, id ResponseType) (*Button, error) {
  	cstr := C.CString(text)
  	defer C.free(unsafe.Pointer(cstr))
  	c := C.gtk_dialog_add_button(v.native(), (*C.gchar)(cstr), C.gint(id))
  	if c == nil {
  		return nil, nilPtrErr
  	}
  	obj := glib.Take(unsafe.Pointer(c))
  	return wrapButton(obj), nil
  }
docs: // AddButton() is a wrapper around gtk_dialog_add_button().  text may
  // be either the literal button text, or if using GTK 3.8 or earlier, a
  // Stock type converted to a string.