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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 start(self):
 """Initialize the worker boot sequence and start up all the worker threads. """

        self.broker.emit_before("worker_boot", self)

        worker_middleware = _WorkerMiddleware(self)
        self.broker.add_middleware(worker_middleware)
        for _ in range(self.worker_threads):
            self._add_worker()

        self.broker.emit_after("worker_boot", self)