@Override
      public Object call() throws Exception {
        QueryObserver observer = QueryObserverHolder.getInstance();
        assertTrue(QueryObserverHolder.hasObserver());
        assertTrue(observer instanceof QueryResultTrackingObserver);
        QueryResultTrackingObserver resultObserver = (QueryResultTrackingObserver) observer;
        assertTrue(resultObserver.isObjectSerialized());
        return null;
      }
Used for saving & restoring oldObserver without serialization
geode-core/src/distributedTest/java/org/apache/geode/cache/query/dunit/SelectStarQueryDUnitTest.java