public function setCoverLetter($coverLetter): DeliveryOptions
    {
        if (!in_array($coverLetter, static::getOptionsForCoverLetter())) {
            throw new InvalidArgumentException(
                sprintf('Property %s is not supported for %s', $coverLetter, __FUNCTION__)
            );
        }

        $this->data['coverLetter'] = $coverLetter;

        return $this;
    }