How to use the @jupyter-widgets/controls.DescriptionView.extend function in @jupyter-widgets/controls

_model_name: 'TreeModel',
    _view_name: 'TreeView',
    _model_module: 'jupyter_cadquery',
    _view_module: 'jupyter_cadquery',
    _model_module_version: "v0.9.5",
    _view_module_version: "v0.9.5",
    icons: null,
    tree: null,
    state: null
  })
});


// TreeView

var TreeView = DescriptionView.extend({
  initialize: function (parameters) {
    DescriptionView.prototype.initialize.apply(this, arguments);

    this.icons = this.model.get("icons");
    // Be sure to work on deep copy, otherwise object will be updated and
    // model.set will not find any differences and nothing will be sent to python!
    this.states = clone(this.model.get("state"));
    this.treeModel = this.toModel(this.model.get("tree"));

    this.listenTo(this.model, "change:state", () => this.updateAllStates());
  },

  render: function () {
    var ul = tag("ul", ["toplevel"]);
    ul.appendChild(this.toHtml(this.treeModel));
    this.el.appendChild(ul);