class_docstr: A very simple `DataLoader` that is mostly used for testing.
code: def _iter_batches(self) -> Iterator[TensorDict]:
      if self.shuffle:
          random.shuffle(self.instances)
      for batch in lazy_groups_of(
          self.iter_instances(), self.batch_size
      ):
          tensor_dict = self.collate_fn(batch)
          if self.cuda_device is not None:
              tensor_dict = nn_util.move_to_device(
                  tensor_dict, self.cuda_device
              )
          yield tensor_dict
  
imports: import math
  import random
  from typing import Optional, List, Iterator
  import torch
  from allennlp.common.util import lazy_groups_of
  from allennlp.common.tqdm import Tqdm
  from allennlp.data.data_loaders.data_loader import DataLoader, TensorDict
  from allennlp.data.data_loaders.data_collator import DefaultDataCollator
  from allennlp.data.dataset_readers import DatasetReader
  from allennlp.data.instance import Instance
  from allennlp.data.vocabulary import Vocabulary
  import allennlp.nn.util
label_desc: Use image node_id 4 for calling the SimpleDataLoader obj's underlying member method code with example usage: obj._iter_batches() without return types