+ using ValueType = VT;
+ using Clock = CT;
+ using Duration = typename Clock::duration;
+ using TimePoint = typename Clock::time_point;
+ // The legacy TimeType. The older code used this instead of Duration and
+ // TimePoint. This will eventually be removed as the code is transitioned to
+ // Duration and TimePoint.
+ using TimeType = typename Clock::duration;
+ using Level = folly::BucketedTimeSeries<ValueType, Clock>;