code: def test_call_cudnn_backward(self):
      with chainer.using_config("use_cudnn", self.use_cudnn):
          with chainer.using_config(
              "cudnn_deterministic", self.cudnn_deterministic
          ):
              y = self.forward()
              y.grad = self.gy
              name = "cupy.cudnn.convolution_backward_data"
              with testing.patch(name) as func:
                  y.backward()
                  self.assertEqual(func.called, self.should_call_cudnn)
  
imports: import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  import chainer.functions
  from chainer import testing
  from chainer.testing import attr
  from chainer.testing import backend
label_desc: Use image node_id 4 for calling the TestConvolution2DCudnnCall obj's underlying member method code with example usage: obj.test_call_cudnn_backward() without return types