class_docstr: Average pooling over a set of 2d planes.
code: def backward(self, indexes, gy):
      return AveragePooling2DGrad(self).apply(gy)
  
imports: import numpy
  import chainer
  from chainer import backend
  from chainer.backends import cuda
  from chainer.backends import intel64
  from chainer import function_node
  from chainer.functions.pooling import average_pooling_nd
  from chainer.functions.pooling import pooling_2d
  from chainer.utils import conv
  import chainerx
label_desc: Use image node_id 4 for calling the AveragePooling2D obj's underlying member method code with example usage: obj.backward(indexes, gy) and returns: AveragePooling2DGrad