revert ids change

      input_files = [input_files]

    def shard_generator():  # TODO Enable sharding with shard size parameter

      for i, input_file in enumerate(input_files):

      for input_file in input_files:

        if self.legacy:

          X = encode_bio_sequence(input_file)

        else:

          sequences = _read_file(input_file)

          X = self.featurizer(sequences)

        ids = np.ones(len(X) * i)

        ids = np.ones(len(X))

        # (X, y, w, ids)

        yield X, None, None, ids