@Override
    public String toString() {
        return "TimeWindow{" +
                "windowSlotSize=" + windowSlotSize +
                ", from=" + from +
                ", to=" + to +
                ", windowRangeCount=" + windowRangeCount +
                '}';
    }
converts the timestamp to the matching window slot's reference timestamp

@param timestamp
@return
commons-timeseries/src/main/java/com/navercorp/pinpoint/common/timeseries/window/TimeWindow.java