https://www.bilibili.com/video/av20961661/?p=1 https://jalammar.github.io/ https://kexue.fm/archives/4765#Position%20Embedding https://blog.youkuaiyun.com/qq_42208267/article/details/84967446 https://blog.youkuaiyun.com/qq_42208267/article/details/84939661 https://www.jianshu.com/p/3f2d4bc126e6