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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _kill_worker_threads(self):
 """ Kill any currently executing worker threads. See :meth:`ServiceContainer.spawn_worker` """

        num_workers = len(self._worker_threads)

        if num_workers:
            _log.warning('killing %s active workers(s)', num_workers)
            for worker_ctx, gt in list(self._worker_threads.items()):
                _log.warning('killing active worker for %s', worker_ctx)
                gt.kill()