How to use the vendors.css function in vendors

export default function render(req, res, next, assetManifest, chunkManifest) {
  axios.defaults.baseURL = `http://${req.clientConfig.host}:${req.clientConfig.port}`;
  let styles = '';

  let scripts = `
  
  `;

  const isProd = process.env.NODE_ENV === 'production';
  if(isProd) {
    styles = `
    
    
  `;

    scripts = `
    
    
    
  `
  }

  const history = createMemoryHistory();
  const authenticated = false;
  //const authenticated = req.isAuthenticated();

  const user = null;

  /*storeInitialState.user.authenticated = authenticated;

//eslint-disable-next-line
const manifest = require("../../dist/client/manifest.json");

const vendorCss = [manifest["vendors.css"], manifest["browser.css"]];
const vendorJs = [manifest["vendors.js"], manifest["browser.js"]];

export default ({ html, preState, helmet, bundles }) => {
  let styles = bundles.filter(bundle => bundle.file.endsWith(".css"));
  let scripts = bundles.filter(bundle => bundle.file.endsWith(".js"));

  return `