public JsonFields<AgentNameView, List<TimeHistogramViewModel>> getTimeSeries() {
        AgentTimeHistogram histogram = new AgentTimeHistogram(application, agentHistogramList);
        return histogram.createViewModel(format);
    }
@return JsonFields(String:AgentId, value:List<TimeViewModel>)
web/src/main/java/com/navercorp/pinpoint/web/view/ApplicationTimeHistogramViewModel.java