code: def test_key_added(self):
      key = torchbearer.state_key("key")
      self.assertTrue("key" in torchbearer.state.__keys__)
  
imports: import unittest
  import warnings
  import torchbearer
  from torchbearer.state import State
label_desc: Use image node_id 4 for calling the TestStateKey obj's underlying member method code with example usage: obj.test_key_added() without return types