private function phoneNumberCountry(PhoneNumber $phoneNumber = null)
    {
        if ($phoneNumber) {
            return $this->phoneNumberUtil->getRegionCodeForNumber($phoneNumber);
        }

        return null;
    }
private function phoneNumberCountry(PhoneNumber $phoneNumber = null)
    {
        if ($phoneNumber) {
            return $this->phoneNumberUtil->getRegionCodeForNumber($phoneNumber);
        }

        return null;
    }
Returns the region code for the given phone number.

@param PhoneNumber|null $phoneNumber

@return string|null