TDAT:     private void updateMean(V parentEntry) {
        assert (!isLeaf());
        int[] weights = new int[count()];
        for (int iChild = 0; iChild < count(); ++iChild) {
            weights[iChild] = children.get(iChild).totalCount;
        }
        parentEntry.updateMean(keys, weights);
    }
 COM: <s> update the means entries based on child entries 1 level down the tree </s>