def start(self, max_transitions=None, keep_active=False):
self._active = True<EOL>self._max_transitions = max_transitions<EOL>self._keep_active = keep_active<EOL>self.thread = Thread(target=self._start_loop)<EOL>self.thread.start()<EOL>
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