def hparams(self, defaults, unused_model_hparams):
    """Returns problem_hparams.

    Args:
      defaults: default hyperparameters
      unused_model_hparams: model hyperparameters

    """

    p = defaults
    p.modality = {"inputs": modalities.ModalityType.SYMBOL,
                  "targets": modalities.ModalityType.CLASS_LABEL}
    p.vocab_size = {"inputs": self._encoders["inputs"].vocab_size,
                    "targets": self._encoders["targets"].vocab_size}
Returns problem_hparams.

    Args:
      defaults: default hyperparameters
      unused_model_hparams: model hyperparameters

    
tensor2tensor/data_generators/lambada.py