code: def __next__(self):
      if self.counter == self.size:
          raise StopIteration
      value = self.step * self.counter
      self.counter += 1
      return value
  
file_path: pytorch-lightning/tests/tests_data/streaming/test_combined.py
imports: import pytest
  from lightning.data.streaming.combined import CombinedStreamingDataset
  from torch.utils.data import IterableDataset
label_desc: Use image node_id 4 for calling the TestStatefulDataset obj's underlying member method code with example usage: obj.__next__() and returns: value