public Optional<Number> eval(JMXMetricHolder jmxMetricHolder) {
      List<Object> metrics = jmxMetricHolder.findAll(propertyList);
      if (metrics.isEmpty()) {
        return Optional.empty();
      } else {
        Object value = getValue().eval(metrics);
        return value instanceof Number ? Optional.of((Number)value) : Optional.empty();
      }
    }
Represents the {@code jmx} element in a Metric alert.
ambari-server/src/main/java/org/apache/ambari/server/state/alert/MetricSource.java