@Override
    public List<T> subList(int fromIndex, int toIndex) {
      return delegatee.subList(fromIndex, toIndex);
    }
This test is for HBASE-26494, test the {@link RefCnt} behaviors in {@link ImmutableMemStoreLAB}
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHStore.java