项目需要，先简记cell，有时间再写具体改进原因
RNN cell
LSTM cell:
GRU cell:
reference:
1、https://towardsdatascience.com/animated-rnn-lstm-and-gru-ef124d06cf45#50f0
2、https://towardsdatascience.com/illustrated-guide-to-lstms-and-gru-s-a-step-by-step-explanation-44e9eb85bf21
RNN, LSTM, GRU cells
原文：https://www.cnblogs.com/qinduanyinghua/p/11393581.html
