public function setGender($genderKey)
    {
        $validGenderKeys = [self::GENDER_MALE, self::GENDER_FEMALE, self::GENDER_UNKNOWN];
        if (!in_array($genderKey, $validGenderKeys, true)) {
            throw new \InvalidArgumentException(
                '$genderKey must be one of the predefined constants, but actually is: ' . $genderKey,
                1393329321
            );
        }

        $this->setAsInteger('gender', $genderKey);
    }