code: def test_get_backend(self):
      ds = RandomDataset()
      collate_fn = Collator(backend="auto")
      paddle_dl = DataLoader(ds, collate_fn=collate_fn)
      for batch in paddle_dl:
          print(batch)
  
file_path: fastNLP/tests/core/dataloaders/paddle_dataloader/test_fdl.py
imports: import pytest
  import numpy
  from fastNLP.core.dataloaders.paddle_dataloader.fdl import PaddleDataLoader, prepare_paddle_dataloader
  from fastNLP.core.dataset import DataSet
  from fastNLP.io.data_bundle import DataBundle
  from fastNLP.core.log import logger
  from fastNLP.core.collators import Collator
  from fastNLP.envs.imports import _NEED_IMPORT_PADDLE
label_desc: Use image node_id 4 for calling the TestPaddle obj's underlying member method code with example usage: obj.test_get_backend() without return types