private void init(List<KafkaMetric> metrics) {
            log.info("initializing Kafka metrics collector");
            for (KafkaMetric m : metrics) {
                metricMap.put(metricNamingStrategy.metricKey(m.metricName()), m);
            }
        }
Keeps track of the state of metrics, e.g. when they were added, what their getAndSet value is,
and clearing them out when they're removed.
clients/src/main/java/org/apache/kafka/common/telemetry/internals/KafkaMetricsCollector.java