<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def stop(self):
 """ Stop the container gracefully. First all entrypoints are asked to ``stop()``. This ensures that no new worker threads are started. It is the extensions' responsibility to gracefully shut down when ``stop()`` is called on them and only return when they have stopped. After all entrypoints have stopped the container waits for any active workers to complete. After all active workers have stopped the container stops all dependency providers. At this point there should be no more managed threads. In case there are any managed threads, they are killed by the container. """

        if self._died.ready():
            _log.debug('already stopped %s', self)
            return

        if self._being_killed:
            # this race condition can happen when a container is hosted by a
            # runner and yields during its kill method; if it's unlucky in
            # scheduling the runner will try to stop() it before self._died
            # has a result
            _log.debug('already being killed %s', self)
            try:
                self._died.wait()
            except:
                pass  # don't re-raise if we died with an exception
            return

        _log.debug('stopping %s', self)

        with _log_time('stopped %s', self):

            # entrypoint have to be stopped before dependencies to ensure
            # that running workers can successfully complete
            self.entrypoints.all.stop()

            # there might still be some running workers, which we have to
            # wait for to complete before we can stop dependencies
            self._worker_pool.waitall()

            # it should be safe now to stop any dependency as there is no
            # active worker which could be using it
            self.dependencies.all.stop()

            # finally, stop remaining extensions
            self.subextensions.all.stop()

            # any any managed threads they spawned
            self._kill_managed_threads()

            self.started = False

            # if `kill` is called after `stop`, they race to send this
            if not self._died.ready():
                self._died.send(None)