code: def _parse_detailpage_html(self, doc):
          
          result = {
              'exts': [],
              'downloadpage_link': ''
          }
          soup = bs4.BeautifulSoup(doc, 'lxml')
          li_list = soup.select('ul.subtitle-info > li')
          for li in li_list:
              if li.string and '【格式】' in li.string:
                  s = li.string.lower()
                  for ext in self.SUPPORT_EXTS:
                      if ext in s:
                          result['exts'].append(ext)
  
          a = soup.select('.subtitle-links > a')
          if a:
              a = a[0]
              result['downloadpage_link'] = a.get('href')
  
          return result
docs: 解析字幕详情页面