docs: def url_quote_plus(s, charset='utf-8', safe=''):
      """URL encode a single string with the given encoding and convert
      whitespace to "+".
  
      :param s: the string to quote.
      :param charset: the charset to be used.
      :param safe: an optional sequence of safe characters.
      """
      if isinstance(s, unicode):
          s = s.encode(charset)
      elif not isinstance(s, str):
          s = str(s)
      return _quote_plus(s, safe=safe)