How to use the @lumino/widgets.CommandPalette function in @lumino/widgets

});

  let rendermime = new RenderMimeRegistry({ initialFactories });

  let editorFactory = editorServices.factoryService.newInlineEditor;
  let contentFactory = new ConsolePanel.ContentFactory({ editorFactory });
  let consolePanel = new ConsolePanel({
    rendermime,
    manager,
    path,
    contentFactory,
    mimeTypeService: editorServices.mimeTypeService
  });
  consolePanel.title.label = TITLE;

  let palette = new CommandPalette({ commands });

  let panel = new SplitPanel();
  panel.id = 'main';
  panel.orientation = 'horizontal';
  panel.spacing = 0;
  SplitPanel.setStretch(palette, 0);
  SplitPanel.setStretch(consolePanel, 1);
  panel.addWidget(palette);
  panel.addWidget(consolePanel);

  // Attach the panel to the DOM.
  Widget.attach(panel, document.body);

  // Handle resize events.
  window.addEventListener('resize', () => {
    panel.update();

export function createPalette(app: JupyterFrontEnd): CommandPalette {
    if (!palette) {
      palette = new CommandPalette({ commands: app.commands });
      palette.id = 'command-palette';
      palette.title.label = 'Commands';
    }

    return palette;
  }
}

let menu2 = createMenu();
  menu2.title.label = 'Edit';
  menu2.title.mnemonic = 0;

  let menu3 = createMenu();
  menu3.title.label = 'View';
  menu3.title.mnemonic = 0;

  let bar = new MenuBar();
  bar.addMenu(menu1);
  bar.addMenu(menu2);
  bar.addMenu(menu3);
  bar.id = 'menuBar';

  let palette = new CommandPalette({ commands });
  palette.addItem({ command: 'example:cut', category: 'Edit' });
  palette.addItem({ command: 'example:copy', category: 'Edit' });
  palette.addItem({ command: 'example:paste', category: 'Edit' });
  palette.addItem({ command: 'example:one', category: 'Number' });
  palette.addItem({ command: 'example:two', category: 'Number' });
  palette.addItem({ command: 'example:three', category: 'Number' });
  palette.addItem({ command: 'example:four', category: 'Number' });
  palette.addItem({ command: 'example:black', category: 'Number' });
  palette.addItem({ command: 'example:new-tab', category: 'File' });
  palette.addItem({ command: 'example:close-tab', category: 'File' });
  palette.addItem({ command: 'example:save-on-exit', category: 'File' });
  palette.addItem({ command: 'example:open-task-manager', category: 'File' });
  palette.addItem({ command: 'example:close', category: 'File' });
  palette.addItem({ command: 'example:clear-cell', category: 'Notebook Cell Operations' });
  palette.addItem({ command: 'example:cut-cells', category: 'Notebook Cell Operations' });
  palette.addItem({ command: 'example:run-cell', category: 'Notebook Cell Operations' });