class_docstr: Explicitly coordinate the level Tornado components required to run a
  Bokeh server:
  
  * A Tornado ``IOLoop`` to run the Bokeh server machinery.
  
  * a ``BokehTornado`` Tornado application that defines the Bokeh server
    machinery.
  
  * a Tornado ``HTTPServer`` to direct HTTP requests
  
  All three of these components must be passed to ``BaseServer``, which will
  initialize the ``BokehTornado`` instance on the ``io_loop``. The
  ``http_server`` must have been previously created and initialized with the
  ``BokehTornado`` instance.
docstr: Get an active a session by name application path and session ID.
  
  Args:
      app_path (str) :
          The configured application path for the application to return
          a session for.
  
      session_id (str) :
          The session ID of the session to retrieve.
  
  Returns:
      ServerSession
docstr_tok: ["Get","an","active","a","session","by","name","application","path","and","session","ID",".","Args",":","app_path","(","str",")",":","The","configured","application","path","for","the","application","to","return","a","session","for",".","session_id","(","str",")",":","The","session","ID","of","the","session","to","retrieve",".","Returns",":","ServerSession"]
code: def get_session(self, app_path: str, session_id: ID) -> ServerSession:
      """Get an active a session by name application path and session ID.
  
      Args:
          app_path (str) :
              The configured application path for the application to return
              a session for.
  
          session_id (str) :
              The session ID of the session to retrieve.
  
      Returns:
          ServerSession
  
      """
      return self._tornado.get_session(app_path, session_id)
  
imports: from __future__ import annotations
  import logging
  import atexit
  import signal
  import socket
  import sys
  from types import FrameType
  from typing import TYPE_CHECKING, Any, Mapping
  from tornado import netutil, version
  from tornado.httpserver import HTTPServer
  from tornado.ioloop import IOLoop
  from ..None import __version__
  from ..core import properties
  from ..core.properties import Bool, Int, Nullable, String
  from ..resources import DEFAULT_SERVER_PORT, server_url
  from ..util.options import Options
  from .tornado import DEFAULT_WEBSOCKET_MAX_MESSAGE_SIZE_BYTES, BokehTornado
  from .util import bind_sockets, create_hosts_allowlist
label_desc: Use image node_id 7 for calling the BaseServer obj's underlying member method code with example usage: obj.get_session(app_path, session_id) and returns: self