code: def url(server: Server, prefix: str = "") -> str:
      return f"http://localhost:{server.port}{prefix}/"
  
imports: from __future__ import annotations
  import logging
  from typing import TYPE_CHECKING, Any
  from tornado.httpclient import AsyncHTTPClient, HTTPRequest
  from tornado.websocket import WebSocketClientConnection, websocket_connect
label_desc: Use image node_id 1 for calling a global function with example usage: url(server, prefix) and returns: str, server, prefix, str