code: private function getManufacturerIdentifier(array $product)
      {
          $manufacturerIdentity = $this->identityService->findOneOrCreate(
              (string) $product['manufacturerId'],
              PlentymarketsAdapter::NAME,
              Manufacturer::TYPE
          );
  
          if (null === $manufacturerIdentity) {
              throw new NotFoundException('missing mapping for manufacturer');
          }
  
          return $manufacturerIdentity->getObjectIdentifier();
      }
docs: @param array $product
  
  @return string