code: def get_default_data_dir(
      given_data_dir: Optional[str] = None,
      dataset: Optional[str] = None,
  ) -> str:
      """Returns the default data_dir."""
      if given_data_dir:
          return os.path.expanduser(given_data_dir)
      elif "TFDS_DATA_DIR" in os.environ:
          return os.environ["TFDS_DATA_DIR"]
      else:
          del dataset
          return constants.DATA_DIR
  
imports: import collections
  import functools
  import os
  import re
  import time
  from typing import Iterator, List, Optional
  from absl import logging
  from etils import epath
  from tensorflow_datasets.core import constants
  from tensorflow_datasets.core import naming
  from tensorflow_datasets.core.utils import docs
  from tensorflow_datasets.core.utils import py_utils
  from tensorflow_datasets.core.utils import read_config
  from tensorflow_datasets.core.utils import type_utils
  from tensorflow_datasets.core.utils import version
label_desc: Use image node_id 4 for calling a global function with example usage: get_default_data_dir(given_data_dir, dataset) and returns: os, os, constants