docs: def splits(cls, text_field, root='.data', train='wiki.train.tokens',
                 validation='wiki.valid.tokens', test='wiki.test.tokens',
                 **kwargs):
          """Create dataset objects for splits of the WikiText-2 dataset.
  
          This is the most flexible way to use the dataset.
  
          Arguments:
              text_field: The field that will be used for text data.
              root: The root directory that the dataset's zip archive will be
                  expanded into; therefore the directory in whose wikitext-2
                  subdirectory the data files will be stored.
              train: The filename of the train data. Default: 'wiki.train.tokens'.
              validation: The filename of the validation data, or None to not
                  load the validation set. Default: 'wiki.valid.tokens'.
              test: The filename of the test data, or None to not load the test
                  set. Default: 'wiki.test.tokens'.
          """
          return super(WikiText2, cls).splits(
              root=root, train=train, validation=validation, test=test,
              text_field=text_field, **kwargs)