code: def stop(self):
      if self.__callback is not None:
          self.__callback.stop()
  
imports: import json
  import time
  import threading
  import six
  from ws4py.client import tornadoclient
  import tornado
  import pyalgotrade.logger
label_desc: Use image node_id 6 for calling the KeepAliveMgr obj's underlying member method code with example usage: obj.stop() without return types