code: def test_get_batch_indices(self):
      ds = DataSet(
          {
              "x": [[1, 2], [2, 3, 4], [4, 5, 6, 7]] * 10,
              "y": [1, 0, 1] * 10,
          }
      )
      fdl = OneflowDataLoader(ds, batch_size=3, shuffle=True)
      for batch in fdl:
          assert len(fdl.get_batch_indices()) == 3
  
file_path: fastNLP/tests/core/dataloaders/oneflow_dataloader/test_fdl.py
imports: import pytest
  from fastNLP.core.dataloaders.oneflow_dataloader import OneflowDataLoader, prepare_oneflow_dataloader
  from fastNLP.core.dataset import DataSet
  from fastNLP.io.data_bundle import DataBundle
  from fastNLP.envs.imports import _NEED_IMPORT_ONEFLOW
  from tests.helpers.utils import Capturing, recover_logger
  from fastNLP import logger
  import numpy
label_desc: Use image node_id 3 for calling the TestFdl obj's underlying member method code with example usage: obj.test_get_batch_indices() without return types