def format_repeated_pair_list(self, key, root_list, level):
        """
        Process (possibly) repeated lists of pairs e.g. POINTs blocks
        """

        lines = []

        def depth(L):
            return isinstance(L, (tuple, list)) and max(map(depth, L)) + 1

        if depth(root_list) == 2:
            # single set of points only
            root_list = [root_list]

        for pair_list in root_list:
            lines += self.format_pair_list(key, pair_list, level)

        return lines