code: def validation_step(self, val_batch, batch_idx):
      loss = self.forward(val_batch)
      self.loss.append(loss)
      return {"val_loss": loss}
  
imports: import torch
  import torch.nn
  import torch.nn.functional
  from torch.utils.data import DataLoader
  from torchmetrics import Accuracy
  from ray import train
  from ray.train.lightning._lightning_utils import import_lightning
label_desc: Use image node_id 4 for calling the LinearModule obj's underlying member method code with example usage: obj.validation_step(val_batch, batch_idx) and returns: dict