docs: public final int[] getIndexRootsArray() {
  
          PersistentStore store =
              database.persistentStoreCollection.getStore(this);
          int[] roots = new int[getIndexCount()];
  
          for (int i = 0; i < getIndexCount(); i++) {
              CachedObject accessor = store.getAccessor(indexList[i]);
  
              roots[i] = accessor == null ? -1
                                          : accessor.getPos();
          }
  
          return roots;
      }