Create the key to sort on the sorted set references in
        self._sort_by_sortedset and adapte sort options

def _prepare_sort_by_score(self, values, sort_options):
        """
        Create the key to sort on the sorted set references in
        self._sort_by_sortedset and adapte sort options
        """
        # create the keys
        base_tmp_key, tmp_keys = self._zset_to_keys(
                                    key=self._sort_by_sortedset['by'],
                                    values=values,
                                    )
        # ask to sort on our new keys
        sort_options['by'] = '%s:*' % base_tmp_key

        # retrieve original sort parameters
        for key in ('desc', 'alpha', 'get', 'store'):
            if key in self._sort_by_sortedset:
                sort_options[key] = self._sort_by_sortedset[key]

        # if we want to get the score with values/values_list
        if sort_options.get('get'):
            try:
                pos = sort_options['get'].index(SORTED_SCORE)
            except:
                pass
            else:
                sort_options['get'][pos] = '%s:*' % base_tmp_key

        return base_tmp_key, tmp_keys