class_docstr: Example taken from Chainer docs:
  
  See: https://docs.chainer.org/en/stable/guides/functions.html
code: def backward_gpu(self, inputs, grad_outputs):
      x, y, z = inputs
      (gw,) = grad_outputs
  
      gx, gy = cuda.elementwise(
          "T x, T y, T gw",
          "T gx, T gy",
          """
                 gx = y * gw;
                 gy = x * gw;
              """,
          "muladd_bwd",
      )(x, y, 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 4 for calling the MulAdd obj's underlying member method code with example usage: obj.backward_gpu(inputs, grad_outputs) and returns: gx,  gy,  gz