code: def test_cam_loss(self):
      key = "my_key"
      targets_hot = torch.FloatTensor([[0, 0, 0, 1, 0]]).ge(0.5)
      decay = 0.5
      loss = imaging.inside_cnns._cam_loss(key, targets_hot, decay)
  
      model = MagicMock
      model.input_image = torch.ones(5, 5) * 2
  
      state = {
          "my_key": torch.FloatTensor([[0, 0, 0, 100, 0]]),
          torchbearer.MODEL: model,
      }
      res = loss(state)
      self.assertTrue(res.item() == -50)
  
file_path: torchbearer/tests/callbacks/imaging/test_inside_cnns.py
imports: from unittest import TestCase
  from mock import MagicMock, patch, ANY
  import torch
  import torchbearer
  import torchbearer.callbacks.imaging
label_desc: Use image node_id 4 for calling the TestClassAppearanceModel obj's underlying member method code with example usage: obj.test_cam_loss() without return types