text: /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
  'use strict';
  
  const models = exports.models = new WeakMap();
  const views = exports.views = new WeakMap();
  exports.buttons = new WeakMap();
  
  exports.viewsFor = function viewsFor(sidebar) views.get(sidebar);
  exports.modelFor = function modelFor(sidebar) models.get(sidebar);
  