code: def start(self):
      # Check every second.
      self.__callback = tornado.ioloop.PeriodicCallback(
          self._keepAlive, 1000
      )
      self.__callback.start()
  
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 5 for calling the KeepAliveMgr obj's underlying member method code with example usage: obj.start() without return types