图解Transformer

https://blog.csdn.net/qq_41664845/article/details/84969266
http://nlp.seas.harvard.edu/2018/04/03/attention.html#attention
http://nlp.seas.harvard.edu/2018/04/03/attention.html#attention
https://towardsdatascience.com/how-to-code-the-transformer-in-pytorch-24db27c8f9ec