code: private MetricValues fdMetricValues(Set<MachineMetric> customSet,
              List<Long> values) {
          return metricValues(customSet, MachineMetricFactory.fdMetrics, values);
      }
docs: Returns the set of file-descriptor metrics and the corresponding values based on
  the default and the customized set of metrics, if any.
  
  @param customSet
  a non-null customized set of metrics
  @param values
  a non-null list of values corresponding to the list of default
  file-descriptor metrics