private Map<String, Histogram> createAgentLevelResponseTime(List<ResponseTime> responseHistogramList) {
            Map<String, Histogram> agentHistogramMap = new HashMap<>();
            for (ResponseTime responseTime : responseHistogramList) {
                for (Map.Entry<String, TimeHistogram> entry : responseTime.getAgentHistogram()) {
                    addAgentLevelHistogram(agentHistogramMap, entry.getKey(), entry.getValue());
                }
            }
            return agentHistogramMap;
        }
this class is a collection of
applicationHistogram
agentHistogram
applicationTimeHistogram
agentTimeHistogram

@author emeroad
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/histogram/NodeHistogram.java