public function getDescendants($className) {
        $descendants = array();
        if (isset($this->classMap[$className])) {
            $descendants = $this->classMap[$className];
            if ($descendants) {
                foreach ($descendants as $descendant) {
                    $descendants = array_merge($descendants, $this->getDescendants($descendant));
                }
            }
        }
        return $descendants;
    }