code: public static Parser<Void> notAmong(String chars) {
      if (chars.length() == 0) return ANY_CHAR;
      if (chars.length() == 1) return notChar(chars.charAt(0));
      return isChar(CharPredicates.notAmong(chars));
    }
docs: A scanner that succeeds and consumes the current character if it is not equal to any character
  in {@code chars}.