  DownstreamTiming& downstreamTiming() override {
    if (!downstream_timing_.has_value()) {
      downstream_timing_ = DownstreamTiming();
    }
    return downstream_timing_.value();
  }
  DownstreamTiming& downstreamTiming() override {
    if (!downstream_timing_.has_value()) {
      downstream_timing_ = DownstreamTiming();
    }
    return downstream_timing_.value();
  }