text: define([
      'base/js/namespace'
  ], function(Jupyter) {
      'use strict';
  
      // taken from https://jupyter-notebook.readthedocs.io/en/stable/extending/frontend_extensions.html
  
      return { onload: function() {
              // Jupyter.keyboard_manager.command_shortcuts.remove_shortcut('0,0');
              Jupyter.keyboard_manager.command_shortcuts.add_shortcut('9,0', 'jupyter-notebook:restart-kernel-and-clear-output');
  
              // var handler = function () {
              //     alert('testing !!!');
              // };
              // var action = {
              //     icon: 'fa-comment-o', // a font-awesome class used on buttons, etc
              //     help: 'Show an alert',
              //     help_index: 'zz',
              //     handler: handler
              // };
              // var prefix = 'my_extension';
              // var action_name = 'show-alert';
              // var full_action_name = Jupyter.actions.register(action, action_name, prefix); // returns 'my_extension:show-alert'
  
              // Jupyter.toolbar.add_buttons_group([full_action_name]);
          }
      }
  })