code: def _handle_tb(_req, tb_servers, key):
      with tb_servers:
          try:
              return tb_servers[key]
          except KeyError as e:
              raise NotFound() from e
  
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 15 for calling a global function with example usage: _handle_tb(_req, tb_servers, key) and returns: tb_servers