code: def _kill_worker_threads(self):
          
          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()
docs: Kill any currently executing worker threads.
  
          See :meth:`ServiceContainer.spawn_worker`