code: private <E> E fetch(Class<E> entityClass, Key nativeKey) {
      try {
        Entity nativeEntity = nativeReader.get(nativeKey);
        E entity = Unmarshaller.unmarshal(nativeEntity, entityClass);
        entityManager.executeEntityListeners(CallbackType.POST_LOAD, entity);
        return entity;
      } catch (DatastoreException exp) {
        throw new EntityManagerException(exp);
      }
    }
docs: Fetches the entity given the native key.
  
  @param entityClass
  the expected result type
  @param nativeKey
  the native key
  @return the entity with the given key, or <code>null</code>, if no entity exists with the given
  key.