code: func (v *Notebook) GetGroupName() (string, error) {
  	c := C.gtk_notebook_get_group_name(v.native())
  	if c == nil {
  		return "", errors.New("No group name")
  	}
  	return goString(c), nil
  }
docs: // GetGroupName() is a wrapper around gtk_notebook_get_group_name().