How to use the next-server/dist/server/utils.isBlockedPage function in next-server

server.get('/*', async (req, res, next) => {
    try {
      // @NOTE code duplication from here
      // https://github.com/zeit/next.js/blob/cc6fe5fdf92c9c618a739128fbd5192a6d397afa/packages/next-server/server/next-server.ts#L405
      const pathName = req.originalUrl;
      if (isInternalUrl(req.url)) {
        return app.handleRequest(req, res, req.originalUrl)
      }

      if (isBlockedPage(pathName)) {
        return app.render404(req, res, req.originalUrl)
      }

      // Provide react-router static router with a context object
      // https://reacttraining.com/react-router/web/guides/server-rendering
      req.locals = {};
      req.locals.context = {};
      const html = await app.renderToHTML(req, res, '/', {});

      // Handle client redirects
      const context = req.locals.context;
      if (context.url) {
        return res.redirect(context.url)
      }

      // Handle client response statuses