code: def _ensure_archive(archive_name, source_dir):
      if source_dir is None:
          _raise_imagenet_error(
              "You must provide a `source_dir` in order to load the ImageNet "
              "dataset."
          )
  
      archive_path = os.path.join(source_dir, archive_name)
      if not os.path.isfile(archive_path):
          _raise_imagenet_error(
              "Archive '%s' not found in directory '%s'."
              % (archive_name, source_dir)
          )
  
label_desc: Use image node_id 2 for calling a global function with example usage: _ensure_archive(archive_name, source_dir) without return types