public function delete($id)
 {
     if (!$this->deleteById($id)) {
         return false;
     }
     $product_services = new shopProductServicesModel();
     $product_services->deleteByField('service_variant_id', $id);
     return true;
 }
 public function deleteServices($product_id, $sku_id)
 {
     $product_services_model = new shopProductServicesModel();
     return $product_services_model->deleteByField(array('product_id' => $product_id, 'sku_id' => $sku_id));
 }