code: def wait_for_ready(self):
      url_base = util.local_server_url(self.host, self.port)
      while not self._ready:
          ping_url = f"{url_base}/assets/favicon.png"
          try:
              util.http_get(ping_url)
          except util.HTTPConnectionError:
              time.sleep(0.1)
          else:
              self._ready = True
  
imports: import json
  import logging
  import math
  import os
  import socket
  import subprocess
  import sys
  import threading
  import time
  from werkzeug.exceptions import NotFound
  from werkzeug.utils import redirect
  from guild import serving_util
  from guild import util
  from guild import var
label_desc: Use image node_id 3 for calling the DevServer obj's underlying member method code with example usage: obj.wait_for_ready() without return types