*
     * <p>Since the last element of the array is actually in the middle of the sorted structure, a
     * childless aunt node could be smaller, which would corrupt the invariant if this element
     * becomes the new parent of the aunt node. In that case, we first switch the last element with
     * its aunt node, before returning.
     */
    int swapWithConceptuallyLastElement(E actualLastElement) {