code: def forward(self, pred, target):
      return torch.tensor(3.0)
  
imports: import copy
  import unittest
  import torch
  from classy_vision.losses import build_loss, ClassyLoss, register_loss, SumArbitraryLoss
label_desc: Use image node_id 1 for calling the MockLoss3 obj's underlying member method code with example usage: obj.forward(pred, target) and returns: torch