class_docstr: Example taken from Chainer docs:
  
  See: https://docs.chainer.org/en/stable/guides/functions.html
code: def backward_cpu(self, inputs, grad_outputs):
      x, y, z = inputs
      (gw,) = grad_outputs
  
      gx = y * gw
      gy = x * gw
      gz = gw
      return gx, gy, gz
  
file_path: chainerrl/chainerrl/functions/mul_add.py
imports: import chainer
  from chainer import cuda
label_desc: Use image node_id 2 for calling the MulAdd obj's underlying member method code with example usage: obj.backward_cpu(inputs, grad_outputs) and returns: gx,  gy,  gz