code: def validation_step(self, batch, batch_idx):
      with torch.no_grad():
          output = self.forward(batch)
          self.calculate_loss(output, tag="valid")
          self.calculate_metrics(output, tag="valid")
      return output
  
imports: import warnings
  from abc import ABCMeta, abstractmethod
  from typing import Dict, Optional
  import pytorch_lightning
  import torch
  import torch.nn
  from omegaconf import DictConfig, OmegaConf
  from pytorch_tabular.models.base_model import _create_optimizer
  from pytorch_tabular.utils import get_logger, getattr_nested, reset_all_weights
label_desc: Use image node_id 15 for calling the SSLBaseModel obj's underlying member method code with example usage: obj.validation_step(batch, batch_idx) and returns: output