How to use the @jupyter-widgets/base.StyleModel function in @jupyter-widgets/base

// Copyright (c) Jupyter Development Team.
// Distributed under the terms of the Modified BSD License.

const widgets = require('@jupyter-widgets/base');
const L = require('./leaflet.js');
const utils = require('./utils.js');

const DEFAULT_LOCATION = [0.0, 0.0];

export class LeafletMapStyleModel extends widgets.StyleModel {
  defaults() {
    return {
      ...super.defaults(),
      _model_name: 'LeafletMapStyleModel',
      _model_module: 'jupyter-leaflet'
    };
  }
}

LeafletMapStyleModel.styleProperties = {
  cursor: {
    selector: '.leaflet-grab',
    attribute: 'cursor',
    default: 'grab'
  }
};

menu.settingsMenu.addGroup([
      {command: '@jupyter-widgets/jupyterlab-manager:saveWidgetState'}
    ]);
  }

  WIDGET_REGISTRY.push({
    name: '@jupyter-widgets/base',
    version: base.JUPYTER_WIDGETS_VERSION,
    exports: {
      WidgetModel: base.WidgetModel,
      WidgetView: base.WidgetView,
      DOMWidgetView: base.DOMWidgetView,
      DOMWidgetModel: base.DOMWidgetModel,
      LayoutModel: base.LayoutModel,
      LayoutView: base.LayoutView,
      StyleModel: base.StyleModel,
      StyleView: base.StyleView
    }
  });

  WIDGET_REGISTRY.push({
    name: '@jupyter-widgets/controls',
    version: JUPYTER_CONTROLS_VERSION,
    exports: () => {
      return new Promise((resolve, reject) => {
        (require as any).ensure(['@jupyter-widgets/controls'], (require: NodeRequire) => {
          resolve(require('@jupyter-widgets/controls'));
        },
        (err: any) => {
          reject(err);
        },
        '@jupyter-widgets/controls'