code: def test_default_data_dir():
      data_dir = file_utils.get_default_data_dir(given_data_dir=None)
      assert data_dir
      assert isinstance(data_dir, str)
  
file_path: datasets/tensorflow_datasets/core/utils/file_utils_test.py
imports: import os
  import time
  from unittest import mock
  from absl.testing import flagsaver
  from etils import epath
  import pytest
  from tensorflow_datasets import testing
  from tensorflow_datasets.core import naming
  from tensorflow_datasets.core.utils import file_utils
  from tensorflow_datasets.core.utils import read_config
label_desc: Use image node_id 1 for calling a global function with example usage: test_default_data_dir() without return types