Backbone pattern not possible with ES6 Classes

UserView.js

import BaseView from './BaseView';
import listenToMany from '../utils/listenToMany';
import template from '../templates/user';

// Backbone's extend + ES6
export default BaseView.extend({
  template,
  listenToMany
});

// Native ES6 classes. It's definitely a matter
// of preference, but this looks much noisier
// than the combination of Backbone.extend and
// ES6 Object Literal extensions.
export default class UserView extends BaseView {
  get template(){
    return template;
  }
  listenToMany(){
    listenToMany.call(this, ...arguments);
  }
}