import tensorflow as tf

        passage_len = input_shape[1]

        # map decoder inputs to word embeddings
        decoder_inputs = tf.unstack(decoder_inputs, axis=1) # max_enc_steps * [batch_size]
        answer_batch_unstack = tf.unstack(answer_batch, axis=1)

        # initialize all the variables
        state_t_1 = init_state
