/**
  * Append attributes to the list of attributes loaded on the quote_items collection
  *
  * @param QuoteConfig $config
  * @param $attributes
  * @return array
  */
 public function afterGetProductAttributes(QuoteConfig $config, $attributes)
 {
     if ($this->config->getRef1Attribute()) {
         $attributes[] = $this->config->getRef1Attribute();
     }
     if ($this->config->getRef2Attribute()) {
         $attributes[] = $this->config->getRef2Attribute();
     }
     if ($this->config->getUpcAttribute()) {
         $attributes[] = $this->config->getUpcAttribute();
     }
     return array_unique($attributes);
 }
 /**
  * Get Ref2 code for product
  *
  * @param \Magento\Catalog\Model\Product $product
  * @return mixed|null
  */
 public function getRef2ForProduct(\Magento\Catalog\Model\Product $product)
 {
     if ($this->config->getRef2Attribute() && $product->getData($this->config->getRef2Attribute())) {
         return $product->getData($this->config->getRef2Attribute());
     }
     return null;
 }