code: def __iter__(self) -> "_DataFetcher":
      self.iterator = iter(self.combined_loader)
      self.reset()
      return self
  
imports: from typing import Any, Iterator, List, Optional
  from typing_extensions import override
  from lightning.fabric.utilities.data import sized_len
  from lightning.pytorch.utilities.combined_loader import _ITERATOR_RETURN, CombinedLoader
  from lightning.pytorch.utilities.exceptions import MisconfigurationException
label_desc: Use image node_id 4 for calling the _DataFetcher obj's underlying member method code with example usage: obj.__iter__() and returns: self