protected function initializeProductLink(array $attr)
    {

        // load the product/linked product/link type ID
        $productId = $attr[MemberNames::PRODUCT_ID];
        $linkTypeId = $attr[MemberNames::LINK_TYPE_ID];
        $linkedProductId = $attr[MemberNames::LINKED_PRODUCT_ID];

        // try to load the link with the passed product/linked product/link type ID
        if ($entity = $this->loadProductLink($productId, $linkedProductId, $linkTypeId)) {
            return $this->mergeEntity($entity, $attr);
        }

        // simply return the attributes
        return $attr;
    }