code: def test_worker_assignment(self) -> None:
      datapipes = [
          _DummyDataReader(1000, str(idx)) for idx in range(10)
      ]
      all_res = []
      num_workers = 4
      for idx in range(num_workers):
          with patch(
              "torchrec.datasets.utils.get_worker_info"
          ) as get_worker_info:
              get_worker_info.return_value = Mock(
                  id=idx, num_workers=num_workers
              )
              all_res += list(ParallelReadConcat(*datapipes))
      expected_res = []
      for dp in datapipes:
          expected_res += list(dp)
      self.assertEqual(all_res, expected_res)
  
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 1 for calling the TestParallelReadConcat obj's underlying member method code with example usage: obj.test_worker_assignment() without return types