code: def remote_jupyter_proxy_url(port):
      
      base_url = os.environ['EXTERNAL_URL']
      host = urllib.parse.urlparse(base_url).netloc
  
      # If port is None we're asking for the URL origin
      # so return the public hostname.
      if port is None:
          return host
  
      service_url_path = os.environ['JUPYTERHUB_SERVICE_PREFIX']
      proxy_url_path = 'proxy/%d' % port
  
      user_url = urllib.parse.urljoin(base_url, service_url_path)
      full_url = urllib.parse.urljoin(user_url, proxy_url_path)
      return full_url
docs: Callable to configure Bokeh's show method when a proxy must be
      configured.
  
      If port is None we're asking about the URL
      for the origin header.