def METHOD_NAME(self, *args):
    dialog: Gtk.Dialog = self.builder.get_object('dialog_bg_export')
    dialog.set_attached_to(MainController.window())
    dialog.set_transient_for(MainController.window())
    resp = dialog.run()
    dialog.hide()
    if resp == ResponseType.OK:
        dialog = Gtk.FileChooserNative.new(
            "Export as PNG...",
            MainController.window(),
            Gtk.FileChooserAction.SAVE,
            None, None
        )
        add_dialog_png_filter(dialog)
        response = dialog.run()
        fn = dialog.get_filename()
        dialog.destroy()
        if response == Gtk.ResponseType.ACCEPT:
            fn = add_extension_if_missing(fn, 'png')
            self.bgp.to_pil().save(fn)