如何设置Python程序的键和值的限制

class KeyValueStore:
    def __init__(self):
        self._key = None
        self._value = None

    @property
    def key(self):
        return self._key

    @key.setter
    def key(self, value):
        if isinstance(value, str):
            self._key = value
        else:
            raise ValueError("Key must be a string.")

    @property
    def value(self):
        return self._value

    @value.setter
    def value(self, value):
        if isinstance(value, int):
            self._value = value
        else:
            raise ValueError("Value must be an integer.")

# 示例用法
store = KeyValueStore()
store.key = "example"
store.value = 100
print(store.key)   # 输出: example
print(store.value) # 输出: 100

# 错误用法，会抛出异常
store.key = 123   # 抛出 ValueError: Key must be a string.
store.value = "abc"  # 抛出 ValueError: Value must be an integer.