<code>null</code> wildcard).</p><p>The provided listener is a <a href="/api/metrics/type-aliases/listener/metriclistener/"><code>MetricListener</code></a> function, and will be called with a reference to the <a href="/api/metrics/interfaces/metrics/metrics/"><code>Metrics</code></a> object, the <a href="/api/common/type-aliases/identity/id/"><code>Id</code></a> of the <a href="/api/metrics/type-aliases/metric/metric/"><code>Metric</code></a> that changed, the new <a href="/api/metrics/type-aliases/metric/me