Process a received 'Single Frame' frame

def _recv_sf(self, data):
        """Process a received 'Single Frame' frame"""
        self.rx_timer.cancel()
        if self.rx_state != ISOTP_IDLE:
            warning("RX state was reset because single frame was received")
            self.rx_state = ISOTP_IDLE

        length = six.indexbytes(data, 0) & 0xf
        if len(data) - 1 < length:
            return 1

        msg = data[1:1 + length]
        self.rx_queue.put(msg)
        for cb in self.rx_callbacks:
            cb(msg)
        self.call_release()
        return 0