public long getTotalCount() {
        long totalCount = 0;
        for (TimeHistogram timeHistogram : targetHistogramTimeMap.values()) {
            totalCount += timeHistogram.getTotalCount();
        }
        return totalCount;
    }
representation of out/in relationship
@author emeroad
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/rawdata/LinkCallData.java