code: def is_svn_page(html):
      # type: (Union[str, Text]) -> Optional[Match[Union[str, Text]]]
      
      return (re.search(r'<title>[^<]*Revision \d+:', html) and
              re.search(r'Powered by (?:<a[^>]*?>)?Subversion', html, re.I))
docs: Returns true if the page appears to be the index page of an svn repository