class_docstr: Unpooling over a set of 2d planes.
code: def backward(self, indexes, grad_outputs):
      return Unpooling2DGrad(self).apply(grad_outputs)
  
imports: import numpy
  import numpy.lib.stride_tricks
  from chainer import backend
  from chainer.backends import cuda
  from chainer import function_node
  from chainer.functions.pooling import pooling_2d
  from chainer.utils import conv
  from chainer.utils import type_check
label_desc: Use image node_id 5 for calling the Unpooling2D obj's underlying member method code with example usage: obj.backward(indexes, grad_outputs) and returns: Unpooling2DGrad