code: def check_backward(self, x_data, y_grad):
      def f(x):
          return functions.unpooling_2d(
              x, self.ksize, outsize=self.outsize, pad=self.pad
          )
  
      gradient_check.check_backward(
          f,
          x_data,
          y_grad,
          dtype=numpy.float64,
          **self.check_backward_options,
      )
  
imports: import unittest
  import numpy
  import six
  import chainer
  from chainer.backends import cuda
  from chainer import functions
  from chainer import gradient_check
  from chainer import testing
  from chainer.testing import attr
  from chainer_tests.functions_tests.pooling_tests import pooling_nd_helper
label_desc: Use image node_id 5 for calling the TestIntegerScaleUnpooling2D obj's underlying member method code with example usage: obj.check_backward(x_data, y_grad) and returns: functions