  OptRef<const DownstreamTiming> downstreamTiming() const override {
    if (!downstream_timing_.has_value()) {
      return {};
    }
    return {*downstream_timing_};
  }
  OptRef<const DownstreamTiming> downstreamTiming() const override {
    if (!downstream_timing_.has_value()) {
      return {};
    }
    return {*downstream_timing_};
  }