code: def check_border_grad(self, x, expected):
      x = chainer.Variable(x)
      y = functions.clip(x, self.x_min, self.x_max)
      l = functions.sum(y)
      l.backward()
      testing.assert_allclose(x.grad, expected, atol=0, rtol=0)
  
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 2 for calling the TestClipBorderGrad obj's underlying member method code with example usage: obj.check_border_grad(x, expected) without return types