code: def _get_mnist(directory):
    
    for filename in [
        _MNIST_TRAIN_DATA_FILENAME, _MNIST_TRAIN_LABELS_FILENAME,
        _MNIST_TEST_DATA_FILENAME, _MNIST_TEST_LABELS_FILENAME
    ]:
      generator_utils.maybe_download(directory, filename, _MNIST_URL + filename)
docs: Download all MNIST files to directory unless they are there.