code: def test_key_metric(self):
      key = torchbearer.state_key("test")
      state = {key: 4}
  
      self.assertDictEqual(key.process(state), {str(key): 4})
      self.assertDictEqual(key.process_final(state), {str(key): 4})
  
imports: import unittest
  import warnings
  import torchbearer
  from torchbearer.state import State
label_desc: Use image node_id 1 for calling the TestStateKey obj's underlying member method code with example usage: obj.test_key_metric() without return types