import tensorflow as tf

      with tf.variable_scope("root", initializer=tf.constant_initializer(0.5)):
        cell = tf.nn.rnn_cell.GRUCell(2)
        inp = tf.constant(0.5, shape=[2, 2, 2])
        enc_outputs, enc_state = tf.nn.dynamic_rnn(cell, inp, dtype=tf.float32)
        attn_states = enc_outputs
        dec_inp = [tf.constant(0.4, shape=[2, 2])] * 3
        dec, mem = tf.nn.seq2seq.attention_decoder(
            dec_inp, enc_state,
            attn_states, cell, output_size=4)
        sess.run([tf.global_variables_initializer()])
