code: def test_len_and_itertools_chain(self) -> None:
      dataset = RandomRecDataset(
          keys=["feat1", "feat2"],
          batch_size=16,
          hash_size=100,
          ids_per_feature=50,
          num_dense=5,
          num_generated_batches=-1,
          num_batches=5,
      )
      self.assertEqual(len(dataset), 5)
      it = itertools.chain(iter(dataset), iter(dataset))
      for _ in range(10):
          next(it)
      self.assertRaises(StopIteration, lambda: next(it))
  
file_path: torchrec/torchrec/datasets/tests/test_random.py
imports: import itertools
  import unittest
  from torchrec.datasets.random import RandomRecDataset
label_desc: Use image node_id 5 for calling the RandomDataLoader obj's underlying member method code with example usage: obj.test_len_and_itertools_chain() without return types