class_docstr: Hosts an application "instance" (an instantiated Document) for one or more connections.
  
      
class_docstr_tok: ["Hosts","an","application","``","instance","''","(","an","instantiated","Document",")","for","one","or","more","connections","."]
docstr: This should only be called by ``ServerConnection.subscribe_session`` or our book-keeping will be broken
code: def subscribe(self, connection: ServerConnection) -> None:
      """This should only be called by ``ServerConnection.subscribe_session`` or our book-keeping will be broken"""
      self._subscribed_connections.add(connection)
  
imports: from __future__ import annotations
  import logging
  import inspect
  import time
  from copy import copy
  from functools import wraps
  from typing import TYPE_CHECKING, Any, Awaitable, Callable, TypeVar
  from tornado import locks
  from ..events import ConnectionLost
  from ..util.token import generate_jwt_token
  from .callbacks import DocumentCallbackGroup
label_desc: Use image node_id 13 for calling the ServerSession obj's underlying member method code with example usage: obj.subscribe(connection) without return types