code: def test_invalid_tuple_type_4th(self):
      with six.assertRaisesRegex(self, RuntimeError, "4th.*int"):
          functions.forget(lambda: (self.v,) * 3 + (1,))
  
imports: import functools
  import unittest
  import numpy
  import six
  import chainer
  from chainer import cuda
  from chainer import functions
  from chainer import gradient_check
  from chainer import links
  from chainer import testing
  from chainer.testing import attr
  from chainer import variable
label_desc: Use image node_id 7 for calling the TestForgetError obj's underlying member method code with example usage: obj.test_invalid_tuple_type_4th() without return types