code: @SuppressWarnings("unchecked")
  	private <T extends Number> List<Metric<T>> filterCounters(Iterable<Metric<?>> input) {
  		List<Metric<T>> result = new ArrayList<>();
  		for (Metric<?> metric : input) {
  			if (metric.getName().startsWith(COUNTER_PREFIX)) {
  				result.add((Metric<T>) metric);
  			}
  		}
  		return result;
  	}
docs: Filter the list of Boot metrics to only return those that are counters.