code: func (v *Window) GetTransientFor() (*Window, error) {
  	c := C.gtk_window_get_transient_for(v.native())
  	if c == nil {
  		return nil, nilPtrErr
  	}
  	return wrapWindow(glib.Take(unsafe.Pointer(c))), nil
  }
docs: // GetTransientFor is a wrapper around gtk_window_get_transient_for().