docs: def on_view_not_found(
              self, _,
              start_response: Callable[[str, List[Tuple[str, str]]], None],
      ) -> Iterable[bytes]:
          """ called when valid view is not found """
  
          start_response(
              "405 Method Not Allowed",
              [('Content-type', 'text/plain')])
          return [b"Method Not Allowed"]