How to use the next-server/dist/server/normalize-page-path.normalizePagePath function in next-server

async ensurePage (page) {
      await this.waitUntilReloaded()
      let normalizedPagePath
      try {
        normalizedPagePath = normalizePagePath(page)
      } catch (err) {
        console.error(err)
        throw pageNotFoundError(normalizedPagePath)
      }

      let pagePath = await findPageFile(pagesDir, normalizedPagePath, pageExtensions)

      // Default the /_error route to the Next.js provided default page
      if (page === '/_error' && pagePath === null) {
        pagePath = 'next/dist/pages/_error'
      }

      if (pagePath === null) {
        throw pageNotFoundError(normalizedPagePath)
      }