/**
  * @param $coupon array Coupon object to validate.
  * @return bool Whether cart contains at least one product valid for specified coupon.
  */
 public static function has_valid_products_for_coupon($coupon)
 {
     /* Look through each product in the cart for a valid coupon. */
     foreach (self::$cart_contents as $product) {
         if (JS_Coupons::is_valid_coupon_for_product($coupon['code'], $product)) {
             return true;
         }
     }
     return false;
 }