code: def get_intern_pattern (url):
      
      parts = strformat.url_unicode_split(url)
      scheme = parts[0].lower()
      domain = parts[1].lower()
      domain, is_idn = urlutil.idna_encode(domain)
      # allow redirection www.example.com -> example.com and vice versa
      if domain.startswith('www.'):
          domain = domain[4:]
      if not (domain and scheme):
          return None
      path = urlutil.splitparams(parts[2])[0]
      segments = path.split('/')[:-1]
      path = "/".join(segments)
      if url.endswith('/'):
          path += '/'
      args = list(re.escape(x) for x in (scheme, domain, path))
      if args[0] in ('http', 'https'):
          args[0] = 'https?'
      args[1] = r"(www\.|)%s" % args[1]
      return "^%s://%s%s" % tuple(args)
docs: Return intern pattern for given URL. Redirections to the same
      domain with or without "www." prepended are allowed.