How to use the @aws-cdk/aws-ec2.SubnetType.ISOLATED function in @aws-cdk/aws-ec2

constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);

    // VPC

    const vpc = new Vpc(this, "Vpc", {
      cidr: "10.0.0.0/16",
      natGateways: 0,
      subnetConfiguration: [
        { name: "aasa_isolated", subnetType: SubnetType.ISOLATED }
      ]
    });
    const subnetIds: string[] = [];
    vpc.isolatedSubnets.forEach(subnet => {
      subnetIds.push(subnet.subnetId);
    });

    // SUBNET GROUP

    const dbSubnetGroup: CfnDBSubnetGroup = new CfnDBSubnetGroup(
      this,
      "AuroraSubnetGroup",
      {
        dbSubnetGroupDescription: "Subnet group to AASA Aurora",
        dbSubnetGroupName: "aasa-subnet-group",
        subnetIds