public function create($productId, ProductVariant &$productVariant)
    {
        $data = $productVariant->exportData();
        $endpoint = '/admin/products/'.$productId.'/variants.json';
        $response = $this->request(
            $endpoint, 'POST', array(
            'variant' => $data
            )
        );
        $productVariant->setData($response['variant']);
    }