code: public function get(string $key)
      {
          $parameter = $this->repository->findOneBy(['key' => $key]);
  
          if (!$parameter) {
              throw new OutOfRangeException('Parameter "'.$key.'" does not exist.');
          }
  
          $this->manager->detach($parameter);
  
          return $parameter->getValue();
      }
docs: Get parameter value
  
  @param string $key
  @return mixed
  @throws \OutOfRangeException