import tensorflow as tf

    self.seq_lens = tf.placeholder(tf.int64, [batch_size], name='seq_lens')

    self.x = tf.placeholder(tf.int32, [batch_size, max_sequence_len],
                            name='x')
    self.y = tf.placeholder(tf.float32, [batch_size, out_vocab_size],
                            name='y')
    self.example_weights = tf.placeholder(tf.float32, [batch_size],
                                          name='example_weights')
