code: def test_deleted_invoke_before_training(self):
      class MyExtension(training.Extension):
          pass
  
      ext = MyExtension()
      with self.assertRaises(AttributeError):
          ext.invoke_before_training
  
file_path: chainer/tests/chainer_tests/training_tests/test_extension.py
imports: import unittest
  import pytest
  from chainer import testing
  from chainer import training
label_desc: Use image node_id 3 for calling the TestExtension obj's underlying member method code with example usage: obj.test_deleted_invoke_before_training() without return types