code: def test_iter_style(self):
      class DS(torch.utils.data.IterableDataset):
          def __iter__(self):
              yield from [1, 2, 3]
  
      ds = DS()
      ds = MapDataset(ds, TestMapDataset.map_func)
      self.assertIsInstance(ds, torch.utils.data.IterableDataset)
  
      data = list(iter(ds))
      self.assertEqual(data, [2, 6])
  
imports: import os
  import pickle
  import sys
  import unittest
  from functools import partial
  import torch
  from iopath.common.file_io import LazyPath
  from detectron2 import model_zoo
  from detectron2.config import get_cfg, instantiate
  from detectron2.data import DatasetCatalog, DatasetFromList, MapDataset, ToIterableDataset, build_batch_data_loader, build_detection_test_loader, build_detection_train_loader
  from detectron2.data.common import AspectRatioGroupedDataset, set_default_dataset_from_list_serialize_method
  from detectron2.data.samplers import InferenceSampler, TrainingSampler
label_desc: Use image node_id 3 for calling the TestMapDataset obj's underlying member method code with example usage: obj.test_iter_style() without return types