def get_within_delta(self, key):
        """
        Get a timedelta object from the application configuration following
        the internal convention of::

            <Amount of Units> <Type of Units>

        Examples of valid config values::

            5 days
            10 minutes

        :param key: The config value key
        """
        txt = current_app.config.get(key)
        values = txt.split()
        return timedelta(**{values[1]: int(values[0])})