public function add_to_cart_url($url, $product = null)
 {
     if (WC_Name_Your_Price_Helpers::is_nyp($product)) {
         $url = get_permalink($product->id);
         // disables the ajax add to cart for WC<2.5
         if (!WC_Name_Your_Price_Helpers::is_woocommerce_2_5()) {
             $product->product_type = 'nyp';
         }
     }
     return $url;
 }