code: def onConnectionEstablished(self, event):
      pusher.WebSocketClient.onConnectionEstablished(self, event)
      self.__connected = datetime.datetime.now()
      self.sendPong()
      self.subscribeChannel("invalid channel")
      self.subscribeChannel("order_book")
      self.subscribeChannel("live_trades")
  
imports: import unittest
  import threading
  import datetime
  from pyalgotrade.websocket import pusher
  from pyalgotrade.websocket import client
label_desc: Use image node_id 3 for calling the WebSocketClient obj's underlying member method code with example usage: obj.onConnectionEstablished(event) without return types