code: function createWidget(widgetType, value, description) {
  
          // Create the widget model.
          return manager.new_model({
              model_module: '@jupyter-widgets/controls',
              model_name: widgetType + 'Model',
              model_id: 'widget-1'
          // Create a view for the model.
          }).then(function(model) {
              console.log(widgetType + ' model created');
  
              model.set({
                  description: description || '',
                  value: value,
              });
  
              return  manager.create_view(model);
          }, console.error.bind(console))
          .then(function(view) {
              console.log(widgetType + ' view created');
              manager.display_view(null, view);
              return view;
          }, console.error.bind(console));
      }
docs: Helper function for creating and displaying widgets.
  @return {Promise<WidgetView>}