docs: public static boolean isPrefixFreeCode(final Set<Bits> keySet) {
      final TreeSet<Bits> check = new TreeSet<Bits>();
      for (final Bits code : keySet) {
        final Bits ceiling = check.ceiling(code);
        if (null != ceiling
          && (ceiling.startsWith(code) || code.startsWith(ceiling))) {
          return false;
        }
        final Bits floor = check.floor(code);
        if (null != floor && (floor.startsWith(code) || code.startsWith(floor))) {
          return false;
        }
        check.add(code);
      }
      return true;
    }