code: def get_data_cache_or_nothing(subdir=None):
      cache_root = os.environ.get("NEON_DATA_CACHE_DIR")
  
      if cache_root is None:
          cache_root = ""
      else:
          cache_root = ensure_dirs_exist(
              os.path.join(cache_root, subdir if subdir else "")
          )
  
      return cache_root
  
file_path: neon/neon/util/persist.py
imports: import importlib
  import logging
  import os
  import pkgutil
  import sys
  import appdirs
  from neon.util.compat import pickle, pickle_load
label_desc: Use image node_id 3 for calling a global function with example usage: get_data_cache_or_nothing(subdir) and returns: cache_root