public Builder putMetric(MetricId id, Number value) {
            metrics.put(id, value);
            return this;
        }
Represents a packet of metrics (with meta information) that belong together because they:
<ul>
    <li>share both the same dimensions and consumers, AND</li>
    <li>represent the same source, e.g. a vespa service or the system hardware.</li>
</ul>

@author gjoranv
metrics-proxy/src/main/java/ai/vespa/metricsproxy/metric/model/MetricsPacket.java