Make quitting a bit easier

from __future__ import annotations

import sys

from collections.abc import Callable

from dataclasses import dataclass, field

    def on_card_placed(self, handle_card: Callable[[CardReader], None]) -> None:

        while True:

            line = input("Card ID (int) or 'r' to remove card> ").strip()

            print("Card ID (int) or 'r' to remove card> ", end="", flush=True)

            # Using sys.stdin.readline instead of input seems to avoid 'Fatal Python error: _enter_buffered_busy:

            # could not acquire lock for <_io.BufferedReader name='<stdin>'> at interpreter shutdown,

            # possibly due to daemon threads' on terminate. I don't know why (does input hold a lock on stdin,

            # but readline doesn't?), but given that this is only for the mock mode, I'll accept this for now.

            line = sys.stdin.readline().strip()

            if line.lower() == "r":

                if self._card_id is not None: