code: def _is_cache_dir_appropriate(cache_dir, cache_file):
      
      if os.path.exists(cache_dir):
          files = os.listdir(cache_dir)
          if cache_file in files:
              return True
          return not bool(files)
      return True
docs: Determine if a directory is acceptable for building.
  
      A directory is suitable if any of the following are true:
        - it doesn't exist
        - it is empty
        - it contains an existing build cache