code: def __iter__(self) -> Iterator[Tuple[int, str]]:
      for idx in range(self.num_rows):
          yield idx, self.val
  
imports: import random
  import unittest
  from typing import Any, Iterator, List, Tuple
  from unittest.mock import Mock, patch
  from torch.utils.data import IterDataPipe
  from torchrec.datasets.utils import idx_split_train_val, ParallelReadConcat, rand_split_train_val
label_desc: Use image node_id 2 for calling the _DummyDataReader obj's underlying member method code with example usage: obj.__iter__() without return types