Returns an optional configuration value by its key, or None if it doesn't exist.

        :param str key: The requested configuration key.
        :return: The configuration key's value, or None if one does not exist.
        :rtype: Optional[str]

def get(self, key: str) -> Optional[str]:
        """
        Returns an optional configuration value by its key, or None if it doesn't exist.

        :param str key: The requested configuration key.
        :return: The configuration key's value, or None if one does not exist.
        :rtype: Optional[str]
        """
        return get_config(self.full_key(key))