protected function traverse( \Aimeos\MShop\Catalog\Item\Iface $node, array $counts )
	{
		$count = ( isset( $counts[$node->getId()] ) ? $counts[$node->getId()] : 0 );

		foreach( $node->getChildren() as $child ) {
			$count += $this->traverse( $child, $counts )->count;
		}

		$node->count = $count;
		return $node;
	}