code: def training_step(self, batch, batch_idx):
      x, y = batch
      logits = self.forward(x)
      loss = F.nll_loss(logits, y.long())
      self.log("train_loss", loss)
      return loss
  
imports: import sys
  import torch
  import torchvision.transforms
  from torch.nn import functional
  import torch.nn
  from torchmetrics import Accuracy
  from torchvision.datasets.mnist import MNIST
  from pytorch_lightning import LightningModule
  from clearml import Task
label_desc: Use image node_id 3 for calling the ImageClassifier obj's underlying member method code with example usage: obj.training_step(batch, batch_idx) and returns: loss