void add(MetricValue val) {
            if (val == null) {
                return;
            }
            if (this.val == null) {
                this.val = val;
            } else {
                this.val.add(val);
            }
        }
Produces a flat list of metric entries from a snapshot (which organizes metrics by dimensions)
container-core/src/main/java/com/yahoo/container/jdisc/state/StateHandler.java