Stop the thread, making this object unusable.

def stop(self):
        """Stop the thread, making this object unusable."""
        if not self._dead:
            self._killed = True
            self._cancelled.set()
            self._busy_sem.release()
            self.join()
            if not self._ready_sem.acquire(False):
                warning("ISOTP Timer thread may not have stopped "
                        "correctly")