docstr: Saves input of layer.
docstr_tok: ["Saves","input","of","layer","."]
code: def _save_input(self, mod, i):
      """Saves input of layer."""
      if mod.training:
          self.state[mod]["x"] = i[0]
  
imports: from copy import deepcopy
  from unittest.mock import DEFAULT, Mock, patch
  import pytest
  import torch
  from lightning.pytorch import Trainer
  from lightning.pytorch.core.optimizer import LightningOptimizer
  from lightning.pytorch.demos.boring_classes import BoringModel
  from lightning.pytorch.loops.optimization.automatic import Closure
  from lightning.pytorch.tuner.tuning import Tuner
  from torch.optim import SGD, Adam, Optimizer
label_desc: Use image node_id 2 for calling the OptimizerWithHooks obj's underlying member method code with example usage: obj._save_input(mod, i) without return types