code: public static RubyRange<Character> range(char start, char end) {
      return new RubyRange<>(CharacterSuccessor.getInstance(), start, end,
          Interval.CLOSED);
    }
docs: Creates a {@link RubyRange} by given chars.
  
  @param start
  of the range
  @param end
  of the range
  @return {@link RubyRange}