code: def forward_cpu(self, inputs):
      self.retain_inputs((0, 1, 2, 3))
      p, x, y, gz = inputs
      pg = p * gz
      return (
          utils.force_array((x - y) * gz),
          utils.force_array(pg),
          utils.force_array(gz - pg),
      )
  
file_path: chainer/chainer/functions/math/linear_interpolate.py
imports: from chainer.backends import cuda
  from chainer import function_node
  from chainer import utils
  from chainer.utils import type_check
label_desc: Use image node_id 1 for calling the LinearInterpolateGrad obj's underlying member method code with example usage: obj.forward_cpu(inputs) and returns: utils,  utils,  utils