code: def enable_selfalias(config, id_name):
      
  
      def context_found_subscriber(event):
          request = event.request
          user = getattr(request, 'user', None)
          if (request.matchdict and
                  request.matchdict.get(id_name, None) == 'self' and
                  user):
              request.matchdict[id_name] = user.username
  
      config.add_subscriber(context_found_subscriber, ContextFound)
docs: This allows replacing id_name with "self".
      e.g. /users/joe/account == /users/self/account if joe is in the session
      as an authorized user