Function wrapper

python/python3/tornado/web.py:1877–1890

(  # type: ignore
        self: RequestHandler, *args, **kwargs
    )

    @functools.wraps(method)
    def wrapper(  # type: ignore
        self: RequestHandler, *args, **kwargs
    ) -> Optional[Awaitable[None]]:
        if self.request.path.endswith("/"):
            if self.request.method in ("GET", "HEAD"):
                uri = self.request.path.rstrip("/")
                if uri:  # don't try to redirect '/' to ''
                    if self.request.query:
                        uri += "?" + self.request.query
                    self.redirect(uri, permanent=True)
                    return None
            else:
                raise HTTPError(404)
        return method(self, *args, **kwargs)

    return wrapper