import tensorflow as tf

        with tf.variable_scope(
            "root", initializer=tf.constant_initializer(0.5)):
          cell = tf.nn.rnn_cell.BasicLSTMCell(2, state_is_tuple=True)
          cell = tf.nn.rnn_cell.MultiRNNCell(cells=[cell] * 2,
                                             state_is_tuple=True)
          inp = tf.constant(0.5, shape=[2, 2, 2])
          enc_outputs, enc_state = tf.nn.rnn(cell, inp, dtype=tf.float32)
          attn_states = tf.concat(1, [tf.reshape(e, [-1, 1, cell.output_size])
                                      for e in enc_outputs])
          dec_inp = [tf.constant(0.4, shape=[2, 2])] * 3
          dec, mem = tf.nn.seq2seq.attention_decoder(
              dec_inp, enc_state,
