How to use the @accounts/database-manager.DatabaseManager function in @accounts/database-manager

console.error('createApolloAccounts: db is a required parameter')
  }
  if (!givenOptions.tokenSecret) {
    console.log(
      'Warning: Must provide a tokenSecret (long random string) to createApolloAccounts()'
    )
  }

  const mongoStorage = new MongoDBInterface(db, {
    convertUserIdToMongoObjectId: false,
    convertSessionIdToMongoObjectId: false,
    idProvider,
    dateProvider
  })

  const dbManager = new DatabaseManager({
    sessionStorage: mongoStorage,
    userStorage: mongoStorage
  })

  const options = defaultsDeep(givenOptions, defaultOptions)

  const accountsServer = new AccountsServer(
    { db: dbManager, ...options },
    {
      password: new AccountsPassword()
    }
  )

  // full list of hooks:
  // https://github.com/accounts-js/accounts/blob/master/packages/server/src/utils/server-hooks.ts
  accountsServer.on('LoginSuccess', callOnLoginHooks)

const start = async () => {
  // Create database connection
  await mongoose.connect('mongodb://localhost:27017/accounts-js-graphql-example', {
    useNewUrlParser: true,
  });
  const mongoConn = mongoose.connection;

  // Build a storage for storing users
  const userStorage = new MongoDBInterface(mongoConn);
  // Create database manager (create user, find users, sessions etc) for accounts-js
  const accountsDb = new DatabaseManager({
    sessionStorage: userStorage,
    userStorage,
  });

  const accountsPassword = new AccountsPassword({
    // This option is called when a new user create an account
    // Inside we can apply our logic to validate the user fields
    validateNewUser: user => {
      // For example we can allow only some kind of emails
      if (user.email.endsWith('.xyz')) {
        throw new Error('Invalid email');
      }
      return user;
    },
  });

const storage = await Object.keys(databasePackages).reduce(
    async (res, packageName: string): Promise => {
      const requiredPackage = requirePackage(packageName);
      if (requiredPackage) {
        return (databasePackages as any)[packageName](requiredPackage);
      }
      return res;
    },
    Promise.resolve([])
  );

  if (!storage) {
    throw new Error('A database package could not be loaded. Did you install one?');
  }

  options.db = new DatabaseManager({
    userStorage: storage,
    sessionStorage: storage,
  });

  const servicePackages = {
    ['@accounts/password']: async (requiredPackage: any): Promise => {
      const AccountsPassword = requiredPackage.default;
      return new AccountsPassword(get(options, ['services', 'password']));
    },
  };

  const services = await Object.keys(servicePackages).reduce(
    async (res, packageName: string): Promise => {
      const requiredPackage = requirePackage(packageName);
      if (requiredPackage) {
        const service = await (servicePackages as any)[packageName](requiredPackage);