code: def __iter__(self) -> Iterator[str]:
      return iter(self.d)
  
file_path: pytorch-lightning/tests/tests_pytorch/loops/optimization/test_optimizer_loop.py
imports: from typing import Dict, Generic, Iterator, Mapping, TypeVar
  import pytest
  import torch
  from lightning.pytorch import Trainer
  from lightning.pytorch.demos.boring_classes import BoringModel
  from lightning.pytorch.loops.optimization.automatic import ClosureResult
  from lightning.pytorch.utilities.exceptions import MisconfigurationException
label_desc: Use image node_id 2 for calling the OutputMapping obj's underlying member method code with example usage: obj.__iter__() and returns: iter