docs: def _get_parent_timestamp(dirname, mtime):
      """
      Get the timestamps up the directory tree. All the way to root.
  
      Because they affect every subdirectory.
      """
      parent_pathname = os.path.dirname(dirname)
  
      # max between the parent timestamp the one passed in
      mtime = _max_timestamps(parent_pathname, False, mtime)
  
      if dirname != os.path.dirname(parent_pathname):
          # this is only called if we're not at the root
          mtime = _get_parent_timestamp(parent_pathname, mtime)
  
      return mtime