private TimeHistogram getTimeHistogram(final long timeStamp) {
        final Long refineTimestamp = timeWindow.refineTimestamp(timeStamp);
        TimeHistogram histogram = targetHistogramTimeMap.get(refineTimestamp);
        if (histogram == null) {
            histogram = new TimeHistogram(target.getServiceType(), refineTimestamp);
            targetHistogramTimeMap.put(refineTimestamp, histogram);
        }
        return histogram;
    }
representation of out/in relationship
@author emeroad
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/rawdata/LinkCallData.java