import tensorflow as tf

  def _fill_problem_hparams_features(self, features):
    if features is not None:
      for k, v in six.iteritems(
          problem_hparams_to_features(self._problem_hparams)):
        if k not in features:
          features[k] = tf.constant(v, name=k)

  def infer(self,
            features=None,
            decode_length=50,
