code: def criterion():
      return nn.MSELoss()
  
imports: import sys
  import pytest
  import torch
  from torch import nn
  from torch.utils.data import Dataset
  from kornia.x import Configuration, ObjectDetectionTrainer
  from kornia.x.trainer import Accelerator
label_desc: Use image node_id 3 for calling a global function with example usage: criterion() and returns: nn