old_contents: import Ember from 'ember';
  import AuthenticatedRouteMixin from 'ember-simple-auth/mixins/authenticated-route-mixin';
  
  export default Ember.Route.extend(AuthenticatedRouteMixin, {
    model: function(){
      return this.store.findAll('article');
    }
  });
  
new_contents: import Ember from 'ember';
  import AuthenticatedRouteMixin from 'ember-simple-auth/mixins/authenticated-route-mixin';
  
  export default Ember.Route.extend(AuthenticatedRouteMixin, {
    model() {
      return this.store.findAll('article');
    }
  });
  
subject: update the model function definition to es6 in admin.articles route