code: def __getitem__(self, key: str) -> T:
      return self.d[key]
  
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 4 for calling the OutputMapping obj's underlying member method code with example usage: obj.__getitem__(key) and returns: self