  static std::shared_ptr<Repetition> opt(const std::shared_ptr<Ope> &ope) {
    return std::make_shared<Repetition>(ope, 0, 1);
  }
  static std::shared_ptr<Repetition> opt(const std::shared_ptr<Ope> &ope) {
    return std::make_shared<Repetition>(ope, 0, 1);
  }