seq_len = 20000; n_classes = 4
inputs = ll.Input(shape=(seq_len,))
x = ll.Embedding(len(word_index), 1000)(inputs)
x = ll.LSTM(units=100, activation='relu', return_sequences=True)(x)
outputs = ll.Dense(units = n_classes, activation='softmax')(x)
model = Model(inputs, outputs)
model.summary()