code: def test_get_implemented_callback_mapping(self) -> None:
      callbacks = []
      remaining_callback_hooks = (
          "on_train_start",
          "on_train_epoch_start",
          "on_train_get_next_batch_end",
          "on_train_step_start",
          "on_train_step_end",
          "on_train_epoch_end",
          "on_train_end",
          "on_eval_start",
          "on_eval_epoch_start",
          "on_eval_get_next_batch_end",
          "on_eval_step_start",
          "on_eval_step_end",
          "on_eval_epoch_end",
          "on_eval_end",
          "on_predict_start",
          "on_predict_epoch_start",
          "on_predict_get_next_batch_end",
          "on_predict_step_start",
          "on_predict_step_end",
          "on_predict_epoch_end",
          "on_predict_end",
      )
  
      # pyre-fixme[3]: Return type must be annotated.
      # pyre-fixme[2]: Parameter must be annotated.
      def dummy_fn(x, y):
          print("foo")
  
      for hook in remaining_callback_hooks:
          kwargs = {hook: dummy_fn}
          callbacks.append(Lambda(**kwargs))
  
      implemented_cbs = _get_implemented_callback_mapping(callbacks)
      for hook in remaining_callback_hooks:
          self.assertIn(hook, implemented_cbs)
          self.assertEqual(len(implemented_cbs[hook]), 1)
      self.assertNotIn("on_exception", implemented_cbs)
  
imports: import unittest
  from typing import Set, Union
  from unittest.mock import MagicMock
  from torchtnt.framework._callback_handler import _get_implemented_callback_mapping, CallbackHandler
  from torchtnt.framework.callback import Callback
  from torchtnt.framework.callbacks.lambda_callback import Lambda
  from torchtnt.framework.state import EntryPoint, State
  from torchtnt.framework.unit import TEvalUnit, TPredictUnit, TTrainUnit
  from torchtnt.utils.timer import Timer
label_desc: Use image node_id 2 for calling the CallbackHandlerTest obj's underlying member method code with example usage: obj.test_get_implemented_callback_mapping() without return types