https://blog.wongcw.com/2021/02/01/robinhood%e5%b0%87%e9%99%90%e5%88%b6%e4%ba%a4%e6%98%93%e7%9a%84%e8%82%a1%e7%a5%a8%e6%95%b8%e9%87%8f%e6%b8%9b%e8%87%b38%e5%8f%aa/