protected static function makePricingOptionFareFamilyOverride($fareFamily)
    {
        $opt = [];

        if ($fareFamily !== null) {
            $po = new PricingOptionGroup(PricingOptionKey::OPTION_FARE_FAMILY);
            $po->optionDetail = new OptionDetail([['FF' => $fareFamily]]);

            $opt[] = $po;
        }

        return $opt;
    }