@Override
  protected Collector createCollector(final String help, final String... labelNames) {
    return GaugeWithCallback.builder()
        .name(this.prefixedName)
        .help(help)
        .labelNames(labelNames)
        .callback(this::callback)
        .build();
  }
A Prometheus supplied gauge collector. A supplied gauge collector is one which actual value is
kept outside the metric system, for example in an external library or to calculate the value only
on demand when a metric scrape occurs.
metrics/core/src/main/java/org/hyperledger/besu/metrics/prometheus/PrometheusSuppliedGauge.java