code: func (v *Window) SetTransientFor(parent IWindow) {
  	var pw *C.GtkWindow = nil
  	if parent != nil {
  		pw = parent.toWindow()
  	}
  	C.gtk_window_set_transient_for(v.native(), pw)
  }
docs: // SetTransientFor is a wrapper around gtk_window_set_transient_for().