code: def forward_gpu(self, inputs):
      self.retain_inputs((0,))
      (x,) = inputs
      x_hat = cuda.elementwise(
          "T x, U mean, U inv_std",
          "T x_hat",
          "x_hat = (x - mean) * inv_std",
          "groupnorm_x_hat",
      )(x, self.mean[:, None], self.inv_std[:, None])
      self.retain_outputs((0,))
      return (x_hat,)
  
imports: import numpy
  import chainer
  from chainer import backend
  from chainer.backends import cuda
  from chainer import configuration
  from chainer import function_node
  from chainer.utils import type_check
label_desc: Use image node_id 3 for calling the _XHat obj's underlying member method code with example usage: obj.forward_gpu(inputs) and returns: x_hat