protected function removePriceInfoFromParent(array $parent)
    {
        $parent[Tag::UnitPrice] = 0;
        $parent[Meta::UnitPriceInc] = 0;
        unset($parent[Meta::LineAmount]);
        unset($parent[Meta::LineAmountInc]);
        unset($parent[Meta::LineDiscountAmountInc]);
        return $parent;
    }