code: def _find_most_recent_backup(normal_path: Optional[str]) -> Optional[str]:
      
      if normal_path is None:
          return None
  
      if os.path.exists(normal_path):
          return normal_path
  
      dirname, basename = os.path.split(normal_path)
      root, ext = os.path.splitext(basename)
      backups = [fi for fi in os.listdir(dirname)
                 if fi.startswith(root) and fi.endswith(ext)]
      ts_re = re.compile(r'.*-([0-9]+)' + ext + '$')
  
      def ts_compare(filename):
          match = ts_re.match(filename)
          if not match:
              return -1
          else:
              return int(match.group(1))
  
      backups_sorted = sorted(backups, key=ts_compare)
      if not backups_sorted:
          return None
      return os.path.join(dirname, backups_sorted[-1])
docs: Find the most recent old settings to migrate.
  
      The input is the path to an unqualified settings file - e.g.
      /mnt/usbdrive/config/robotSettings.json
  
      This will return
      - None if the input is None (to support chaining from dict.get())
      - The input if it exists, or
      - The file named normal_path-TIMESTAMP.json with the highest timestamp
        if one can be found, or
      - None