code: def step(self, epoch: Optional[int] = None) -> None:
      ...
  
imports: from pathlib import Path
  from typing import Any, Callable, DefaultDict, Dict, Iterator, List, Optional, Protocol, TypeVar, Union, runtime_checkable
  import torch
  from torch import Tensor
  from torch.optim import Optimizer
  from typing_extensions import TypeAlias, overload
  from lightning.fabric.utilities.imports import _TORCH_GREATER_EQUAL_1_13, _TORCH_GREATER_EQUAL_2_0
label_desc: Use image node_id 2 for calling the LRScheduler obj's underlying member method code with example usage: obj.step(epoch) without return types