How to use the urlscan.urlscan.HTMLChunker.ul_tags function in urlscan

def end_list_para(self):
        if self.at_para_start:
            self.rval.append([])
        if self.list_stack:
            tag = self.list_stack[-1][0]
            if tag == 'ul':
                depth = len([t for t in self.list_stack if t[0] == tag])
                ul_tags = HTMLChunker.ul_tags
                chunk = Chunk('%s  ' % (ul_tags[depth % len(ul_tags)]),
                              self.cur_url())
            else:
                counter = self.list_stack[-1][1]
                self.list_stack[-1] = (tag, counter + 1)
                chunk = Chunk("%2d." % counter, self.cur_url())
            self.add_chunk(chunk)
        else:
            self.end_para()