class_docstr: _NullFuture resembles a Future that finished with a result of None.
  
  It's not actually a `Future` to avoid depending on a particular event loop.
  Handled as a special case in the coroutine runner.
  
  We lie and tell the type checker that a _NullFuture is a Future so
  we don't have to leak _NullFuture into lots of public APIs. But
  this means that the type checker can't warn us when we're passing
  a _NullFuture into a code path that doesn't understand what to do
  with it.
class_docstr_tok: ["_NullFuture","resembles","a","Future","that","finished","with","a","result","of","None",".","It","'s","not","actually","a","`","Future","`","to","avoid","depending","on","a","particular","event","loop",".","Handled","as","a","special","case","in","the","coroutine","runner",".","We","lie","and","tell","the","type","checker","that","a","_NullFuture","is","a","Future","so","we","do","n't","have","to","leak","_NullFuture","into","lots","of","public","APIs",".","But","this","means","that","the","type","checker","ca","n't","warn","us","when","we","'re","passing","a","_NullFuture","into","a","code","path","that","does","n't","understand","what","to","do","with","it","."]
code: def done(self) -> bool:
      return True
  
imports: import asyncio
  import builtins
  import collections
  from collections.abc import Generator
  import concurrent.futures
  import datetime
  import functools
  from functools import singledispatch
  from inspect import isawaitable
  import sys
  import types
  from tornado.concurrent import Future, is_future, chain_future, future_set_exc_info, future_add_done_callback, future_set_result_unless_cancelled
  from tornado.ioloop import IOLoop
  from tornado.log import app_log
  from tornado.util import TimeoutError
  import typing
  from typing import Union, Any, Callable, List, Type, Tuple, Awaitable, Dict, overload
label_desc: Use image node_id 2 for calling the _NullFuture obj's underlying member method code with example usage: obj.done() and returns: True