Given a list of set, combine them to create the final set that will be
        used to make the final redis call.
        If we have a least a sorted set, use zinterstore insted of sunionstore

def _combine_sets(self, sets, final_set):
        """
        Given a list of set, combine them to create the final set that will be
        used to make the final redis call.
        If we have a least a sorted set, use zinterstore insted of sunionstore
        """
        if self._has_sortedsets:
            self.cls.get_connection().zinterstore(final_set, list(sets))
        else:
            final_set = super(ExtendedCollectionManager, self)._combine_sets(sets, final_set)
        return final_set