code: def test_state_dict(self):
      callback = Callback()
  
      self.assertEqual(callback.state_dict(), {})
      self.assertEqual(callback.load_state_dict({}), callback)
  
imports: import unittest
  from mock import Mock, MagicMock, create_autospec, patch
  import torch
  import torchbearer
  from torchbearer.bases import Metric, Callback, base_closure
  from torchbearer.metrics.primitives import CategoricalAccuracy
label_desc: Use image node_id 1 for calling the TestCallback obj's underlying member method code with example usage: obj.test_state_dict() without return types