code: def validation_step(self, batch, batch_idx):
      out = self.model(*batch.inputs)
      loss, _ = self.loss_fn(*out, *batch.labels)
      self.log_metric(batch, out, loss, "val")
      return loss
  
file_path: audio/examples/self_supervised_learning/lightning_modules.py
imports: from collections import namedtuple
  from typing import Callable, Optional
  import lightning.pytorch
  import torch
  import torch.nn
  from torch.optim.optimizer import Optimizer
label_desc: Use image node_id 4 for calling the SSLPretrainModule obj's underlying member method code with example usage: obj.validation_step(batch, batch_idx) and returns: loss