feat: merge PR aimacode#1267

Author: weasdown

deep_learning4e.py

@@ -6,7 +6,7 @@
 import numpy as np
 from keras import Sequential, optimizers
 from keras.layers import Embedding, SimpleRNN, Dense
-from keras.utils import pad_sequences
+from keras.utils import pad_sequences # version 2.9
 
 from utils4e import (conv1D, gaussian_kernel, element_wise_product, vector_add, random_weights,
                      scalar_vector_product, map_vector, mean_squared_error_loss)