How to use the parse-server.S3Adapter function in parse-server

var port = process.env.PORT || 1337;
// Serve the Parse API on the /parse URL prefix
var mountPath = process.env.PARSE_MOUNT || '/parse';
var serverURL = process.env.SERVER_URL || 'http://localhost:' + port + mountPath; // Don't forget to change to https if needed

var S3Adapter = require('parse-server').S3Adapter;
var GCSAdapter = require('parse-server').GCSAdapter;
//var FileSystemAdapter = require('parse-server').FileSystemAdapter;
var filesAdapter;

if (process.env.S3_ACCESS_KEY &&
    process.env.S3_SECRET_KEY &&
    process.env.S3_BUCKET) {
    var directAccess = !!+(process.env.S3_DIRECT);

    filesAdapter = new S3Adapter(
        process.env.S3_ACCESS_KEY,
        process.env.S3_SECRET_KEY,
        process.env.S3_BUCKET,
        {directAccess: directAccess});
} else if (process.env.GCP_PROJECT_ID &&
    process.env.GCP_KEYFILE_PATH &&
    process.env.GCS_BUCKET) {
    var directAccess = !!+(process.env.GCS_DIRECT);

    filesAdapter = new GCSAdapter(
        process.env.GCP_PROJECT_ID,
        process.env.GCP_KEYFILE_PATH,
        process.env.GCS_BUCKET,
        {directAccess: directAccess});
} else if (process.env.AZURE_ACCOUNT &&
    process.env.AZURE_CONTAINER &&

cloud: process.env.CLOUD_CODE_MAIN || __dirname + '/cloud/main.js',
  appId: process.env.APP_ID || 'myAppId',
  masterKey: process.env.MASTER_KEY || '', //Add your master key here. Keep it secret!
  fileKey: process.env.FILE_KEY || '', // Add the file key to provide access to files already hosted on Parse
  serverURL: process.env.SERVER_URL || 'http://localhost:1337/parse',  // Don't forget to change to https if needed
  liveQuery: {
    classNames: ["Posts", "Comments"] // List of classes to support for query subscriptions
  },
  // push: {
  //   android: { senderId: process.env.GCM_SENDER_ID, apiKey: process.env.GCM_API_KEY },
  //   ios: [
  //     { pfx: __dirname + "/push/aps_development.p12", bundleId: process.env.APP_BUNDLE_ID, production: false },
  //     { pfx: __dirname + "/push/aps_production.p12", bundleId: process.env.APP_BUNDLE_ID, production: true }
  //   ]
  // },
  filesAdapter: new S3Adapter(
    process.env.S3_ACCESS_KEY,
    process.env.S3_SECRET_KEY,
    process.env.S3_BUCKET,
    {
      region: process.env.S3_REGION,
      directAccess: process.env.S3_DIRECT_ACCESS
    }
  )
});
// Client-keys like the javascript key or the .NET key are not necessary with parse-server
// If you wish you require them, you can set them as options in the initialization above:
// javascriptKey, restAPIKey, dotNetKey, clientKey

// parse dashboard
var dashboard = new ParseDashboard({
  apps: [