code: def test_step(self, batch, batch_idx):
      x, y = batch
      y_hat = self.backbone(x)
      loss = self.loss(y_hat, y)
      self.log("test_loss", loss)
  
imports: from argparse import ArgumentParser
  import os
  import os.path
  import torch
  import torch.nn
  from torch.nn import functional
  from torch.utils.data import DataLoader
  import pytorch_lightning
  from pytorch_lightning.callbacks import ModelCheckpoint
  from pytorch_lightning.callbacks import LearningRateMonitor
  from pytorch_lightning.loggers import TensorBoardLogger
  import timm
  from datasets.dataset_synthetics import FaceDataset, DataLoaderX
label_desc: Use image node_id 5 for calling the FaceSynthetics obj's underlying member method code with example usage: obj.test_step(batch, batch_idx) without return types