docs: def ucnstring_to_python(ucn_string):
      """
      Return string with Unicode UCN (e.g. "U+4E00") to native Python Unicode
      (u'\\u4e00').
      """
      res = re.findall("U\+[0-9a-fA-F]*", ucn_string)
      for r in res:
          ucn_string = ucn_string.replace(text_type(r), text_type(ucn_to_unicode(r)))
  
      ucn_string = ucn_string.encode('utf-8')
  
      assert isinstance(ucn_string, bytes)
      return ucn_string