public function getQuantity(array $options, $type = null)
    {
        $options += array('order_id' => 0);

        $result = array(
            'total' => 0,
            'sku' => array()
        );

        foreach ((array) $this->getList($options) as $item) {
            $result['total'] += (int) $item['quantity'];
            $result['sku'][$item['sku']] = (int) $item['quantity'];
        }

        if (isset($type)) {
            return $result[$type];
        }

        return $result;
    }