code: def train_batch(self, batch, model, epoch_idx, batch_idx):
      # Figure what the weight should be right now
      w_real = model.weight.data[0]
  
      loss = torch.nn.L1Loss()(model(batch), batch)
  
      return {"loss": loss}
  
file_path: determined/harness/tests/experiment/fixtures/ancient-checkpoints/0.13.13-pytorch-old/code/model_def.py
imports: import torch
  from torch import nn
  from determined.pytorch import DataLoader, PyTorchTrial
label_desc: Use image node_id 4 for calling the OneVarPytorchTrial obj's underlying member method code with example usage: obj.train_batch(batch, model, epoch_idx, batch_idx) and returns: dict