private function isProctoredDelivery(\core_kernel_classes_Resource $delivery)
    {
        $hasProctor = $delivery->getOnePropertyValue($this->getProperty(ProctorService::ACCESSIBLE_PROCTOR));
        $result = $hasProctor instanceof \core_kernel_classes_Resource &&
            $hasProctor->getUri() == ProctorService::ACCESSIBLE_PROCTOR_ENABLED;
        return $result;
    }