https://blog.wongcw.com/2018/12/19/pep-8016-%e7%8d%b2%e5%8b%9d%e6%88%90%e7%82%ba%e6%96%b0%e7%9a%84python-%e7%a4%be%e5%8d%80%e6%b2%bb%e7%90%86%e6%96%b9%e6%a1%88/