code: def on_train_start(
      self, trainer: "pl.Trainer", pl_module: "pl.LightningModule"
  ) -> None:
      if (
          trainer.checkpoint_callback
          and trainer.checkpoint_callback.dirpath is not None
      ):
          self.work.checkpoint_dir = Path(
              trainer.checkpoint_callback.dirpath
          )
  
imports: import inspect
  from typing import TYPE_CHECKING, Any, Dict, Union
  import lightning.pytorch
  from lightning.app.storage.path import Path
  from lightning.app.utilities.app_helpers import Logger
  from lightning.pytorch import Callback
  from lightning.pytorch.callbacks.progress.progress_bar import get_standard_metrics
  from lightning.pytorch.loggers import TensorBoardLogger, WandbLogger
  from lightning.pytorch.utilities.parsing import collect_init_args
  from core.state import ProgressBarState, TrainerState
label_desc: Use image node_id 3 for calling the PLAppArtifactsTracker obj's underlying member method code with example usage: obj.on_train_start(trainer, pl_module) without return types