private function getUnitIdentifier(array $variation)
    {
        if (empty($variation['unit'])) {
            return null;
        }

        // Unit
        $unitIdentity = $this->identityService->findOneBy([
            'adapterIdentifier' => (string) $variation['unit']['unitId'],
            'adapterName' => PlentymarketsAdapter::NAME,
            'objectType' => Unit::TYPE,
        ]);

        if (null === $unitIdentity) {
            throw new NotFoundException('missing mapping for unit');
        }

        return $unitIdentity->getObjectIdentifier();
    }
private function getUnitIdentifier(array $variation)
    {
        if (empty($variation['unit'])) {
            return null;
        }

        // Unit
        $unitIdentity = $this->identityService->findOneBy([
            'adapterIdentifier' => (string) $variation['unit']['unitId'],
            'adapterName' => PlentymarketsAdapter::NAME,
            'objectType' => Unit::TYPE,
        ]);

        if (null === $unitIdentity) {
            throw new NotFoundException('missing mapping for unit');
        }

        return $unitIdentity->getObjectIdentifier();
    }
@param array $variation

@return null|string