code: def on_train_epoch_start(self) -> None:
      if self.freeze_model:
          # Set model to eval mode to disable norm layer updates.
          self.model.eval()
  
file_path: lightly/lightly/utils/benchmarking/linear_classifier.py
imports: from typing import Any, Dict, List, Tuple, Union
  import torch
  from pytorch_lightning import LightningModule
  from torch import Tensor
  from torch.nn import CrossEntropyLoss, Linear, Module
  from torch.optim import SGD, Optimizer
  from lightly.utils.benchmarking.topk import mean_topk_accuracy
  from lightly.utils.scheduler import CosineWarmupScheduler
label_desc: Use image node_id 7 for calling the LinearClassifier obj's underlying member method code with example usage: obj.on_train_epoch_start() without return types