code: public static void addSubStatsToParent(SPIStats parentStats, SPIStats subStats) {
          StatsImpl p = (StatsImpl) parentStats;
          StatsImpl s = (StatsImpl) subStats;
          p.add(s);
      }
docs: This method adds one Stats object as a subStats of another Stats object
  
  @param parentStats This Stats is the parent
  @param subStats This Stats is the child