docs: def extract(self, html):
          "Extract http-equiv refresh url to follow."
          extracted = {}
          soup = BeautifulSoup(html, parser)
          for meta_tag in soup.find_all('meta'):
              if self.key_attr in meta_tag.attrs and 'content' in meta_tag.attrs and \
                  meta_tag[self.key_attr].lower() == self.val_attr:
                  refresh = meta_tag.attrs['content']
                  try:
                      pause, newurl = self.parse_refresh_header(refresh)
                      if newurl:
                          extracted['urls'] = [newurl]
                          break # one is enough
                  except:
                      pass # nevermind
          return extracted