code: def check_backward(self, x_data, W_data, b_data, y_grad):
      args = (x_data, W_data)
      if b_data is not None:
          args = args + (b_data,)
  
      gradient_check.check_backward(
          local_convolution_2d.local_convolution_2d,
          args,
          y_grad,
          **self.check_backward_options,
      )
  
imports: import unittest
  import numpy
  from six import moves
  from chainer import cuda
  from chainer.functions.connection import convolution_2d
  from chainer.functions.connection import local_convolution_2d
  from chainer import gradient_check
  from chainer import testing
  from chainer.testing import attr
  from chainer.testing import condition
label_desc: Use image node_id 7 for calling the TestLocalConvolution2DFunction obj's underlying member method code with example usage: obj.check_backward(x_data, W_data, b_data, y_grad) without return types