'Provides the configuration keys that have never been provided to a caller
via :func:`~stem.util.conf.config_dict` or the
:func:`~stem.util.conf.Config.get` and
:func:`~stem.util.conf.Config.get_value` methods.
:returns: **set** of configuration keys we\'ve loaded but have never been requested'

def unused_keys(self):

    return set(self.keys()).difference(self._requested_keys)
