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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, max_transitions=None, keep_active=False):
 """ Start the driver. This method creates a thread which runs the event loop. The method returns immediately. To wait until the driver finishes, use `stmpy.Driver.wait_until_finished`. `max_transitions`: execute only this number of transitions, then stop `keep_active`: When true, keep the driver running even when all state machines terminated """

        self._active = True
        self._max_transitions = max_transitions
        self._keep_active = keep_active
        self.thread = Thread(target=self._start_loop)
        self.thread.start()