How to use the @vue/component-compiler.assemble function in @vue/component-compiler

'css',
                  'styles',
                  index
                )}'`

              if (style.module || descriptor.styles[index].scoped) {
                return { ...style, code: '', map: undefined }
              }
            })
            .filter(Boolean)
        }

        // Why?
        input.script.code = input.script.code.replace(/^\s+/gm, '')

        const result = assemble(compiler, filename, beforeAssemble(input), opts)

        descriptor.customBlocks.forEach((block, index) => {
          if (!isAllowed(block.type)) return
          const lang =
            typeof block.attrs.lang === 'string'
              ? block.attrs.lang
              : defaultLang[block.type] || block.type
          const id = createVuePartRequest(filename, lang, block.type, index)
          result.code +=
            '\n' +
            `export * from '${id}'\n` +
            `import __custom_block_${index}__ from '${id}'\n` +
            `__custom_block_${index}__(__vue_component__)`
        })

        dT(

return async (req, res, next) => {
    // TODO caching
    if (req.path.endsWith('.vue')) {
      const { filepath, source } = await read(req)
      const descriptorResult = compiler.compileToDescriptor(filepath, source)
      const assembledResult = vueCompiler.assemble(compiler, filepath, descriptorResult)
      res.setHeader('Content-Type', 'application/javascript')
      res.end(assembledResult.code)
    } else if (req.path.endsWith('.js')) {
      const { filepath, source } = await read(req)
      // transform import statements
      const transformed = transformModuleImports(source)
      res.setHeader('Content-Type', 'application/javascript')
      res.end(transformed)
    } else if (req.path.startsWith('/__modules/')) {
      const pkg = req.path.replace(/^\/__modules\//, '')
      const source = await loadPkg(pkg)
      res.setHeader('Content-Type', 'application/javascript')
      res.end(source)
    } else {
      next()
    }

async function bundleSFC (req) {
    const { filepath, source, updateTime } = await readSource(req)
    const descriptorResult = compiler.compileToDescriptor(filepath, source)
    const assembledResult = vueCompiler.assemble(compiler, filepath, {
      ...descriptorResult,
      script: injectSourceMapToScript(descriptorResult.script),
      styles: injectSourceMapsToStyles(descriptorResult.styles)
    })
    return { ...assembledResult, updateTime }
  }