class_docstr: Sum of array elements over a given axis.
code: def backward(self, indexes, grad_outputs):
      (gy,) = grad_outputs
      ndim = len(self.inputs[0].shape)
      if not (ndim == 0 or self.axis is None or self.keepdims):
          actual_axis = [
              axis if axis >= 0 else axis + ndim for axis in self.axis
          ]
          shape = list(gy.shape)
          for axis in sorted(actual_axis):
              shape.insert(axis, 1)
          gy = chainer.functions.reshape(gy, shape)
      return (chainer.functions.broadcast_to(gy, self.inputs[0].shape),)
  
imports: import numpy
  import six
  import chainer
  from chainer import backend
  from chainer import function_node
  from chainer import utils
  from chainer.utils import type_check
  import chainerx
label_desc: Use image node_id 5 for calling the Sum obj's underlying member method code with example usage: obj.backward(indexes, grad_outputs) and returns: chainer