public function flushMemberCache($memberIDs = null)
    {
        $cache = SiteTree::singleton()->getCreatableChildrenCache();

        if (!$memberIDs) {
            $cache->clear();
            return;
        }

        foreach ($memberIDs as $memberID) {
            $key = $this->generateChildrenCacheKey($memberID);
            $cache->delete($key);
        }
    }