code: def update_core_gpu(self, param):
      grad = param.grad
      if grad is None:
          return
      cuda.elementwise(
          "T grad, T lr, T alpha, T eps",
          "T param, T ms",
          """ms = alpha * ms + (1 - alpha) * grad * grad;
                 param -= lr * grad / sqrt(ms + eps);""",
          "rmsprop",
      )(
          grad,
          self.hyperparam.lr,
          self.hyperparam.alpha,
          self.hyperparam.eps,
          param.array,
          self.state["ms"],
      )
  
file_path: chainerrl/chainerrl/optimizers/rmsprop_async.py
imports: from chainer import cuda
  from chainer import optimizer
  import numpy
label_desc: Use image node_id 4 for calling the RMSpropAsyncRule obj's underlying member method code with example usage: obj.update_core_gpu(param) without return types