def clear(self):
        """
        Brutely clears the key value store for keys with THUMBNAIL_KEY_PREFIX
        prefix. Use this in emergency situations. Normally you would probably
        want to use the ``cleanup`` method instead.
        """
        all_keys = self._find_keys_raw(settings.THUMBNAIL_KEY_PREFIX)
        if all_keys:
            self._delete_raw(*all_keys)