How to use the @jupyterlab/notebook.NotebookActions.undo function in @jupyterlab/notebook

it('should redo a cell action', () => {
        const count = widget.widgets.length;
        const next = widget.widgets[1];
        widget.select(next);
        NotebookActions.deleteCells(widget);
        NotebookActions.undo(widget);
        NotebookActions.redo(widget);
        expect(widget.widgets.length).to.equal(count - 2);
      });

it('should switch the widget to command mode', () => {
        widget.mode = 'edit';
        NotebookActions.undo(widget);
        expect(widget.mode).to.equal('command');
      });

    execute: () => NotebookActions.undo(nbWidget.content)
  });

    execute: () => NotebookActions.undo(nbWidget.content)
  });

      execute: () => NotebookActions.undo(nbWidget.content)
    });

execute: args => {
      const current = getCurrent(args);

      if (current) {
        return NotebookActions.undo(current.notebook);
      }
    },
    isEnabled

execute: args => {
      const current = getCurrent(args);

      if (current) {
        return NotebookActions.undo(current.content);
      }
    },
    isEnabled

    execute: () => NotebookActions.undo(nbWidget.notebook)
  });

execute: args => {
      const current = getCurrent(args);

      if (current) {
        return NotebookActions.undo(current.notebook);
      }
    },
    isEnabled

    execute: () => NotebookActions.undo(nbWidget.content)
  });