text: class MaterialCollapsibleDirective {
  
      constructor($timeout) {
          this.restrict = 'A';
          this.$timeout = $timeout;
      }
  
      link(scope, element, attribute, controller) {
          this.$timeout(() => {
              element.collapsible();
          });
      }
  
      static directiveFactory($timeout) {
          MaterialCollapsibleDirective.instance = new MaterialCollapsibleDirective($timeout);
          return MaterialCollapsibleDirective.instance;
      }
  }
  
  MaterialCollapsibleDirective.directiveName = 'materialCollapsible';
  MaterialCollapsibleDirective.$inject = ['$timeout'];
  app.directive(MaterialCollapsibleDirective.directiveName, MaterialCollapsibleDirective.directiveFactory);