code: def test_build_sum_arbitrary(self):
      config = self._get_config()
      crit = build_loss(config)
      self.assertTrue(isinstance(crit, SumArbitraryLoss))
      self.assertAlmostEqual(crit.weights, [1.0, 1.0, 1.0])
      mod_list = [MockLoss1, MockLoss2, MockLoss3]
      for idx, crit_type in enumerate(mod_list):
          self.assertTrue(isinstance(crit.losses[idx], crit_type))
  
imports: import copy
  import unittest
  import torch
  from classy_vision.losses import build_loss, ClassyLoss, register_loss, SumArbitraryLoss
label_desc: Use image node_id 4 for calling the TestSumArbitraryLoss obj's underlying member method code with example usage: obj.test_build_sum_arbitrary() without return types