https://blog.wongcw.com/2019/03/02/memnet%e5%9c%a8%e7%b7%9a%e7%85%a7%e7%89%87%e5%8d%b0%e8%b1%a1%e6%8c%87%e6%95%b8%e6%aa%a2%e6%b8%ac/