Send a message using built-in cyclic transmit list functionality.

def _send_periodic_internal(self, msg, period, duration=None):
        """Send a message using built-in cyclic transmit list functionality."""
        if self._scheduler is None:
            self._scheduler = HANDLE()
            _canlib.canSchedulerOpen(self._device_handle, self.channel,
                                     self._scheduler)
            caps = structures.CANCAPABILITIES()
            _canlib.canSchedulerGetCaps(self._scheduler, caps)
            self._scheduler_resolution = float(caps.dwClockFreq) / caps.dwCmsDivisor
            _canlib.canSchedulerActivate(self._scheduler, constants.TRUE)
        return CyclicSendTask(self._scheduler, msg, period, duration,
                              self._scheduler_resolution)