code: def backward(self, indexes, ggx):
      return UnpoolingND(
          self.ndim,
          self.ksize,
          self.stride,
          self.pad,
          self.outs,
          self.cover_all,
      ).apply(ggx)
  
imports: import numpy
  import six
  from chainer import backend
  from chainer import function_node
  from chainer.functions.pooling import pooling_nd
  from chainer.utils import conv
  from chainer.utils import conv_nd
  from chainer.utils import type_check
label_desc: Use image node_id 3 for calling the UnpoolingNDGrad obj's underlying member method code with example usage: obj.backward(indexes, ggx) and returns: UnpoolingND