code: protected function initializeModel($id, $shardingKey = null)
      {
          if (is_null($this->model)) {
              $this->model = $this->entityManager->load($this->modelClassName, $id, $shardingKey);
          }
  
          return $this;
      }
docs: initialize the unique model
  @param mixed $id
  @param mixed $shardingKey
  
  @return self