code: def check_backward(self, x_data, t_data, gy_data):
      gradient_check.check_backward(
          functions.select_item,
          (x_data, t_data),
          gy_data,
          eps=0.01,
          dtype="d",
          **self.check_backward_options,
      )
  
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 5 for calling the TestSelectItem obj's underlying member method code with example usage: obj.check_backward(x_data, t_data, gy_data) without return types