code: func (v *Notebook) GetNthPage(pageNum int) (*Widget, error) {
  	c := C.gtk_notebook_get_nth_page(v.native(), C.gint(pageNum))
  	if c == nil {
  		return nil, nilPtrErr
  	}
  	return wrapWidget(glib.Take(unsafe.Pointer(c))), nil
  }
docs: // GetNthPage() is a wrapper around gtk_notebook_get_nth_page().