code: def check_backward(self, x, grid, grads):
      gradient_check.check_backward(
          functions.spatial_transformer_sampler,
          (x, grid),
          (grads,),
          dtype="d",
          atol=1e-2,
          rtol=1e-2,
          eps=1e-5,
      )
  
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
  from chainer.testing import condition
  from chainer import Variable
label_desc: Use image node_id 5 for calling the TestSpatialTransformerSampler obj's underlying member method code with example usage: obj.check_backward(x, grid, grads) without return types