}

    /**
     * If the delegate collection is empty, but the multimap has values for the key, replace the
     * delegate with the new collection for the key.
     *
     * <p>For a subcollection, refresh its ancestor and validate that the ancestor delegate hasn't
     * changed.
     */
    void refreshIfEmpty() {
      if (ancestor != null) {
        ancestor.refreshIfEmpty();

    }

    /**
     * If the delegate collection is empty, but the multimap has values for the key, replace the
     * delegate with the new collection for the key.
     *
     * <p>For a subcollection, refresh its ancestor and validate that the ancestor delegate hasn't
     * changed.
     */
    void refreshIfEmpty() {
      if (ancestor != null) {
        ancestor.refreshIfEmpty();