code: def _make_list(predictions, targets):
    
    #  Our models sometimes return predictions in lists, make it a list always.
    # TODO(lukaszkaiser): make abstractions for nested structures and refactor.
    if not isinstance(predictions, (list, tuple)):
      if isinstance(targets, (list, tuple)):
        raise ValueError("Targets are a list or tuple but predictions are not.")
      predictions, targets = [predictions], [targets]
    if len(predictions) != len(targets):
      raise ValueError("Predictions and targets have different lengths.")
    return list(predictions), list(targets)
docs: Helper: make predictions and targets lists, check they match on length.