Update lstm_seq2seq.py(from 22% to 87% acc) (#13269)
Update lstm_seq2seq.py(from 22% to 87% acc) (#13269)

* #13266 Update lstm_seq2seq.py(from 22% to 87% acc)

I added the codes for applying one-hot encoding on the end of sentences about encoder_input_data, decoder_input_data, and decoder_target_data. I added an accuracy metric for model training. The original code has 22% accuracy, but the proposed code had 87% validation accuracy.

* Update lstm_seq2seq.py

I update code according to PEP8.

* Update lstm_seq2seq.py

Remove whitespace according to PEP 8.

keras-team/keras,keras-team/keras