protected function addChild($parent, $child)
    {
        if (is_string($parent)) {
            $parent = $this->findItem($parent);
        }

        if (is_string($child)) {
            $child = $this->findItem($child);
        }

        echo "    > adding $child->name as child to $parent->name ...";
        $time = microtime(true);
        $this->authManager->addChild($parent, $child);
        echo ' done (time: ' . sprintf('%.3f', microtime(true) - $time) . "s)\n";
    }