Ipywidget Gridbox没有输出显示-PYTHON JUPYTER笔记本

Question

我浏览了Ipywidgets文档，发现当我使用GridBox时，Jupyter中没有任何输出 笔记本。

https://ipywidgets.readthedocs.io/en/stable/examples/Widget%20Styling.html#Shorthand-CSS-properties

下面是此代码段的示例。

from ipywidgets import Button, GridBox, Layout, ButtonStyle

header  = Button(description='Header',
             layout=Layout(width='auto', grid_area='header'),
             style=ButtonStyle(button_color='lightblue'))
main    = Button(description='Main',
             layout=Layout(width='auto', grid_area='main'),
             style=ButtonStyle(button_color='moccasin'))
sidebar = Button(description='Sidebar',
             layout=Layout(width='auto', grid_area='sidebar'),
             style=ButtonStyle(button_color='salmon'))
footer  = Button(description='Footer',
             layout=Layout(width='auto', grid_area='footer'),
             style=ButtonStyle(button_color='olive'))

GridBox(children=[header, main, sidebar, footer],
        layout=Layout(
        width='50%',
        grid_template_rows='auto auto auto',
        grid_template_columns='25% 25% 25% 25%',
        grid_template_areas='''
        "header header header header"
        "main main . sidebar "
        "footer footer footer footer"
        '''))

我没有任何输出。有人知道为什么吗？预先非常感谢：）