1.iteriterms和itemgetter
https://blog.youkuaiyun.com/weixin_38705903/article/details/79231577
2.sorted
https://blog.youkuaiyun.com/weixin_38705903/article/details/79231588
3.使用Matplotlib注解绘制树形图
https://blog.youkuaiyun.com/sinat_29957455/article/details/76553987