code: def from_config(cls, config):
      return cls()
  
imports: import copy
  import unittest
  import torch
  from classy_vision.losses import build_loss, ClassyLoss, register_loss, SumArbitraryLoss
label_desc: Use image node_id 2 for calling the MockLoss3 obj's underlying member method code with example usage: obj.from_config(cls, config) and returns: cls