Changes the state of the instance data with the given
        ``key`` and the provided ``value``.

        Wrapping with a decorator is probably not necessary.

        :param key: A ``str`` containing the key to update
        :param value: A value to change the ``key`` to
        :return: None

def change_state(self, key, value):
        """
        Changes the state of the instance data with the given
        ``key`` and the provided ``value``.

        Wrapping with a decorator is probably not necessary.

        :param key: A ``str`` containing the key to update
        :param value: A value to change the ``key`` to
        :return: None
        """
        if key not in VALID_KEYS:
            raise InvalidState
        self._data[key] = value