code: public void sumMetricSnapshot(MetricSnapshot metricSnapshot, MetricSnapshot snapshot) {
          metricSnapshot.set_min(metricSnapshot.get_min() + snapshot.get_min());
          metricSnapshot.set_max(metricSnapshot.get_max() + snapshot.get_max());
          metricSnapshot.set_p50(metricSnapshot.get_p50() + snapshot.get_p50());
          metricSnapshot.set_p75(metricSnapshot.get_p75() + snapshot.get_p75());
          metricSnapshot.set_p95(metricSnapshot.get_p95() + snapshot.get_p95());
          metricSnapshot.set_p98(metricSnapshot.get_p98() + snapshot.get_p98());
          metricSnapshot.set_p99(metricSnapshot.get_p99() + snapshot.get_p99());
          metricSnapshot.set_p999(metricSnapshot.get_p999() + snapshot.get_p999());
          metricSnapshot.set_mean(metricSnapshot.get_mean() + snapshot.get_mean());
          metricSnapshot.set_stddev(metricSnapshot.get_stddev() + snapshot.get_stddev());
      }
docs: sum histograms