code: def test_exception_handler(self):
      ext = ErrorHandlingExtension()
      self.trainer.extend(ext, trigger=(1, "iteration"), priority=1)
      self.assertFalse(ext.is_error_handled)
  
      d = {}
  
      def exception_handler(trainer, exp, tb):
          d["called"] = True
  
      @training.make_extension(
          trigger=(1, "iteration"),
          priority=100,
          on_error=exception_handler,
      )
      def exception_raiser(trainer):
          raise TheOnlyError()
  
      self.trainer.extend(exception_raiser)
  
      dummy_extension = DummyExtension(self)
      self.trainer.extend(dummy_extension)
  
      with self.assertRaises(TheOnlyError):
          self.trainer.run()
  
      self.assertTrue(d["called"])
      self.assertTrue(ext.is_error_handled)
      self.assertTrue(dummy_extension.is_finalized)
  
imports: import time
  import traceback
  import unittest
  from chainer import testing
  from chainer import training
label_desc: Use image node_id 14 for calling the TestTrainer obj's underlying member method code with example usage: obj.test_exception_handler() without return types