code: private static Collection<String> getAvailableMetrics(Collection<? extends MetricStore.ComponentMetricStore> stores) {
  		Set<String> uniqueMetrics = new HashSet<>(32);
  		for (MetricStore.ComponentMetricStore store : stores) {
  			uniqueMetrics.addAll(store.metrics.keySet());
  		}
  		return uniqueMetrics;
  	}
docs: Returns a JSON string containing a list of all available metrics in the given stores. Effectively this method maps
  the union of all key-sets to JSON.
  
  @param stores metrics
  @return JSON string containing a list of all available metrics