code: def check_backward(
      self, x, ksize, stride, pad, cover_all, dilate, gy
  ):
      def f(x):
          return functions.im2col(
              x,
              ksize,
              stride=stride,
              pad=pad,
              cover_all=cover_all,
              dilate=dilate,
          )
  
      gradient_check.check_backward(
          f, x, gy, dtype=numpy.float64, **self.check_backward_options
      )
  
imports: import unittest
  import numpy
  from six import moves
  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.utils.conv import get_conv_outsize
label_desc: Use image node_id 2 for calling the TestIm2Col obj's underlying member method code with example usage: obj.check_backward(x, ksize, stride, pad, cover_all, dilate, gy) and returns: functions