code: public static void addStatisticsToParent(SPIStats parentStats, SPIStatistic statistic) {
          StatsImpl p = (StatsImpl) parentStats;
          StatisticImpl s = (StatisticImpl) statistic;
          p.add(s);
      }
docs: This method adds one Statistic object as the child of a Stats object
  
  @param parentStats This stats is the parent
  @param statistic This statistic should be added