code: def on_validation_epoch_end(self, trainer, pl_module) -> None:
      pl_module.log("latency", pl_module.time_avg)
  
imports: from typing import Any
  import torch
  import time
  from pytorch_lightning.callbacks import Callback
  from pytorch_lightning.loops.dataloader.evaluation_loop import EvaluationLoop
  from bigdl.nano.utils.common import invalidInputError
  from collections import ChainMap
  from torchmetrics import Metric
label_desc: Use image node_id 3 for calling the LatencyCallback obj's underlying member method code with example usage: obj.on_validation_epoch_end(trainer, pl_module) without return types