Help for sql.shutdown_writer

def shutdown_writer():
    """Signal writer thread to exit and wait for it to finish."""
    global _writer_thread
    _writer_shutdown.set()
    # Put enough poison pills for any possible writer threads (usually 1)
    _write_queue.put(None)
    if _writer_thread:
        _writer_thread.join(timeout=2)
        _writer_thread = None  # Allow restart
    # Clean up: clear shutdown flag for future tests
    _writer_shutdown.clear()
    # Drain any leftover queue items (to avoid memory leaks between tests)
    try:
        while True:
            _write_queue.get_nowait()
            _write_queue.task_done()
    except queue.Empty:
        pass