code: def training_step(self, batch, batch_idx):
      x, y = batch
      logits = self(x)
      loss = self.criterion(logits, y)
      self.log("train_loss", loss)
      return loss
  
file_path: nni/examples/compression/evaluator/lightning_evaluator.py
imports: import pytorch_lightning
  from pytorch_lightning.loggers import TensorBoardLogger
  import torch
  from torchmetrics.functional import accuracy
  import nni
  from examples.compression.models import build_resnet18
  from nni.compression import LightningEvaluator
label_desc: Use image node_id 2 for calling the MyModule obj's underlying member method code with example usage: obj.training_step(batch, batch_idx) and returns: loss