def __init__(self):
        self.callback_queue = Queue()
        self._running = False
        self._async = None
        self._state_change = Semaphore()
        self._workers = []
Create a :class:`SequentialGeventHandler` instance
dataset/ETHPy150Open python-zk/kazoo/kazoo/handlers/gevent.py/SequentialGeventHandler.__init__