code: def add(self, x, y):
      time.sleep(3)
      return x + y
  
file_path: PARL/parl/remote/tests/cluster_monitor_2_test.py
imports: import unittest
  import parl
  from parl.remote.monitor import ClusterMonitor
  import time
  import threading
  from parl.remote import exceptions
  from parl.utils.test_utils import XparlTestCase
label_desc: Use image node_id 7 for calling the Actor obj's underlying member method code with example usage: obj.add(x, y) and returns: unknown