def _get_subinfo_list(self, videoname):
        """ return subinfo_list of videoname
        """
        # searching subtitles
        res = self.session.get(self.API, params={'q': videoname})
        doc = res.content
        referer = res.url
        subgroups = self._parse_search_results_html(doc)
        if not subgroups:
            return []
        subgroup = self._filter_subgroup(subgroups)

        # get subtitles
        headers = {
            'Referer': referer
        }
        res = self.session.get(self._join_url(self.API, subgroup['link']), headers=headers)
        doc = res.content
        referer = res.url
        subinfo_list = self._parse_sublist_html(doc)
        for subinfo in subinfo_list:
            subinfo['link'] = self._join_url(res.url, subinfo['link'])
        return subinfo_list, referer
return subinfo_list of videoname