code: def set_extern (self, url):
          
          if self.extern:
              return
          if not url:
              self.extern = (1, 1)
              return
          for entry in self.aggregate.config["externlinks"]:
              match = entry['pattern'].search(url)
              if (entry['negate'] and not match) or \
                 (match and not entry['negate']):
                  log.debug(LOG_CHECK, "Extern URL %r", url)
                  self.extern = (1, entry['strict'])
                  return
          for entry in self.aggregate.config["internlinks"]:
              match = entry['pattern'].search(url)
              if (entry['negate'] and not match) or \
                 (match and not entry['negate']):
                  log.debug(LOG_CHECK, "Intern URL %r", url)
                  self.extern = (0, 0)
                  return
          if self.aggregate.config['checkextern']:
              self.extern = (1, 0)
          else:
              self.extern = (1, 1)
docs: Match URL against extern and intern link patterns. If no pattern
          matches the URL is extern. Sets self.extern to a tuple (bool,
          bool) with content (is_extern, is_strict).
  
          @return: None