code: def __call__(self, environ, start_response):
      path_info = environ.get("PATH_INFO", "")
      script_name = environ.get("SCRIPT_NAME", "")
      _log.debug("PATH INFO  : {0}".format(path_info))
      _log.debug("SCRIPT NAME: {0}".format(script_name))
  
      try:
          if path_info == self.root_path:
              _log.info("Root path requested.")
              start_response("200 OK", [("content-type", "text/html")])
              content = self._root_content()
              return [content.encode("utf-8")]
  
          if path_info == self.shutdown_path:
              _log.info("Shutting down.")
              server = self.config["server"]
              server.stop()
              start_response("200 OK", [("content-type", "text/html")])
              return ["Shutdown".encode("utf-8")]
  
          if path_info == self.favicon_path:
              _log.info("Favicon requested.")
  
              start_response(
                  "200 OK", [("content-type", "image/x-icon")]
              )
              with open(self.favicon_res, "rb") as handler:
                  return [handler.read()]
  
          match = re.search(self.app_pattern, path_info)
          if (
              match is None
              or self.pool.get(match.group(1), None) is None
          ):
              msg = "URL not supported: {0}".format(path_info)
              _log.error(msg)
              start_response(
                  "400 BAD REQUEST ERROR",
                  [("content-type", "text/html")],
              )
              return [msg.encode("utf-8")]
  
          ctx_id = match.group(1)
          _log.info("Routing request: {0}".format(ctx_id))
          app = self.pool[ctx_id]
          if self.base_url and not environ["PATH_INFO"].startswith(
              "/{0}".format(self.base_url)
          ):
              _log.info(
                  "No base url in path. Rewrite to include in path."
              )
              environ["PATH_INFO"] = "/{0}{1}".format(
                  self.base_url, environ["PATH_INFO"]
              )
  
          return app(environ, start_response)
  
      except Exception as e:  # pragma: no cover
          _log.error(e, exc_info=True)
          try:
              start_response(
                  "500 INTERNAL SERVER ERROR",
                  [("Content-Type", "text/plain")],
              )
          except Exception:
              pass
          return [
              "Internal Server Error caught by Dispatcher. See logs if available.".encode(
                  "utf-8"
              )
          ]
  
imports: from IPython import display
  import re
  import requests
  import threading
  import os
  from .None import _udash
  from gevent.pywsgi import WSGIServer
  from flask import Flask
  import socket
  import random
  from string import Template
  import logging
label_desc: Use image node_id 4 for calling the DispatcherApp obj's underlying member method code with example usage: obj.__call__(environ, start_response) and returns: app, list, list, list, list, list