code: def double(self):
      self.val += self.val
  
imports: import pytest
  import time
  import random
  import sys
  import subprocess
  from unittest.mock import patch
  import ray.util.client.server.server
  import ray.core.generated.ray_client_pb2
  from ray.util.client import _ClientContext, CURRENT_PROTOCOL_VERSION
  from ray.cluster_utils import cluster_not_supported
  import ray
label_desc: Use image node_id 2 for calling the C obj's underlying member method code with example usage: obj.double() without return types