def start(self):
        try:
            self.sent_messages = 0
            self.failed_messages = 0
            self.received_messages = 0

            self.info("Connecting and booting via pyGSM...")
            self.modem = pygsm.GsmModem(logger=self.gsm_log, **self.modem_kwargs)
            self.modem.boot()

            if self.service_center in None:
                self.modem.service_center = self.service_center

            # call the superclass to start the run loop -- it just sets
            # ._running to True and calls run, but let's not duplicate it.
            BackendBase.start(self)

        except:
            if getattr(self, "modem", None):
                self.modem.disconnect()

            raise
dataset/ETHPy150Open rapidsms/rapidsms-core-dev/lib/rapidsms/backends/gsm.py/Backend.start/operator `is not` -> `in`