code: public ReturnValue withPerformanceData(final Metric metric, final UnitOfMeasure uom, final String warningRange,
              final String criticalRange) {
          performanceDataList.add(new PerformanceData(metric, uom, warningRange, criticalRange));
          return this;
      }
docs: Adds performance data to the plugin result. Thos data will be added to
  the output formatted as specified in Nagios specifications
  (http://nagiosplug.sourceforge.net/developer-guidelines.html#AEN201)
  
  @param metric
  The metric relative to this result
  @param uom
  The Unit Of Measure
  @param warningRange
  The warning threshold used to check this metric (can be null)
  @param criticalRange
  The critical threshold used to check this value (can be null)
  @return this