code: def add(self, x, y):
      time.sleep(3)
      return x + y
  
imports: import unittest
  import parl
  import time
  import threading
  from parl.remote import exceptions
  import subprocess
  from parl.utils import logger
  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