code: def check_backward(self, x_data, y_grad):
      slices = []
      for i, s in enumerate(self.slices):
          if isinstance(s, numpy.ndarray):
              s = chainer.backends.cuda.cupy.array(s)
          if isinstance(s, list):
              s = chainer.backends.cuda.cupy.array(s, dtype=numpy.int32)
          slices.append(s)
      slices = tuple(slices)
  
      def f(x):
          return functions.get_item(x, slices)
  
      gradient_check.check_backward(f, (x_data,), y_grad, dtype="d")
  
imports: import unittest
  import numpy
  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
label_desc: Use image node_id 4 for calling the TestCupyIndicesGetItem obj's underlying member method code with example usage: obj.check_backward(x_data, y_grad) and returns: functions