activate: (app: JupyterLab, settingRegistry: ISettingRegistry, splash: ISplashScreen): IThemeManager => {
   let baseUrl = app.serviceManager.serverSettings.baseUrl;
   let host = app.shell;
   let when = app.started;
   let manager = new ThemeManager({ baseUrl,  settingRegistry, host, when });
   let disposable = splash.show();
   manager.ready.then(() => {
     setTimeout(() => {
       disposable.dispose();
     }, 2500);
   }, () => {
     disposable.dispose();
   });
   return manager;
 },

      execute: (args: IRouter.ILocation) => {
        const { hash, path, search } = args;
        const query = URLExt.queryStringToObject(search || '');
        const reset = 'reset' in query;
        const clone = 'clone' in query;

        if (!reset) {
          return;
        }

        // If a splash provider exists, launch the splash screen.
        const loading = splash
          ? splash.show()
          : new DisposableDelegate(() => undefined);

        // If the state database has already been resolved, resetting is
        // impossible without reloading.
        if (resolved) {
          return router.reload();
        }

        // Empty the state database.
        resolved = true;
        transform.resolve({ type: 'clear', contents: null });

        // Maintain the query string parameters but remove `reset`.
        delete query['reset'];

        const silent = true;
        const hard = true;
        const url = path + URLExt.objectToQueryString(query) + hash;
        const cleared = commands
          .execute(CommandIDs.recoverState)
          .then(() => router.stop); // Stop routing before new route navigation.

        // After the state has been reset, navigate to the URL.
        if (clone) {
          void cleared.then(() => {
            router.navigate(url, { silent, hard });
          });
        } else {
          void cleared.then(() => {
            router.navigate(url, { silent });
            loading.dispose();
          });
        }

        return cleared;
      }