code: public function findOneBy(array $criteria = [])
      {
          Assertion::isArray($criteria);
  
          $storage = reset($this->storages);
          $identity = $storage->findOneBy($criteria);
  
          if ($identity !== null) {
              $this->validator->validate($identity);
  
              return $identity;
          }
  
          return null;
      }
docs: {@inheritdoc}