Hi All, I am getting errors on my code when I run cdk synth and can't figure out what is wrong. Most of the code is copied from the tutorial or generated by Code Editor. Error message and code below.

from aws_cdk import ( Duration, Stack, SecretValue, aws_ec2 as ec2, aws_rds as rds, aws_iam as iam, aws_elasticloadbalancingv2 as elbv2, ) from constructs import Construct

class CdkappStack(Stack):

def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
    super().__init__(scope, construct_id, **kwargs)

    # create a vpc with IpAddresses 10.10.0.0/16, a NAT gateway, a public subnet, PRIVATE_WITH_EGRESS subnet and a RDS subnet
    vpc = ec2.Vpc(
        self,
        "VPC",
        ip_addresses=ec2.IpAddresses.cidr("10.10.0.0/16"),
        subnet_configuration=[
            ec2.SubnetConfiguration(
                name="Public",
                subnet_type=ec2.SubnetType.PUBLIC,
                cidr_mask=24,
            ),
            ec2.SubnetConfiguration(
                name="PrivateWithEgress",
                subnet_type=ec2.SubnetType.PRIVATE_WITH_EGRESS,
                cidr_mask=24,
            ),
            ec2.SubnetConfiguration(
                name="Private",
                subnet_type=ec2.SubnetType.PRIVATE_ISOLATED,
                cidr_mask=24,
            ),
            ec2.SubnetConfiguration(
                name="RDS",
                subnet_type=ec2.SubnetType.PRIVATE_ISOLATED,
                cidr_mask=24,
            ),
        ],
    )


    # create a security group for the load balancer
    alb_sg = ec2.SecurityGroup(
        self,
        "ALBSG",
        vpc=vpc,
        allow_all_outbound=True,
    )

    # create a security group for the RDS instance
    rds_sg = ec2.SecurityGroup(
        self,
        "RDSSecurityGroup",
        vpc=vpc,
        allow_all_outbound=True,
    )

    # create a security group for the EC2 instance
    ec2_sg = ec2.SecurityGroup(
        self,
        "EC2SecurityGroup",
        vpc=vpc,
        allow_all_outbound=True,
    )

    # add ingress rules for the load balancer security group to allow all traffic on port 80
    alb_sg.add_ingress_rule(
        peer=ec2.Peer.any_ipv4(),
        connection=ec2.Port.tcp(80),
    )
   

    # add ingress rule for the EC2 instance security group to allow 8443 traffic from the load balance
    ec2_sg.add_ingress_rule(
        peer=alb_sg,
        connection=ec2.Port.tcp(8443),
    )

    # add ingress rule to RDS security group to allow 3306 traffic from EC2 security group
    rds_sg.add_ingress_rule(
        peer=ec2_sg,
        connection=ec2.Port.tcp(3306),
    )

    # add ingress rule for the RDS security group to allow 22 from the EC2 instance
    rds_sg.add_ingress_rule(
        peer=ec2_sg,
        connection=ec2.Port.tcp(22),
    )

# create an rds aurora mysql cluster
cluster = rds.DatabaseCluster(self, "MyDatabase",
        engine = rds.DatabaseClusterEngine.aurora_mysql(version = rds.AuroraMysqlEngineVersion.VER_3_04_0),
        # credentials using testuser and password1234!
        credentials = rds.Credentials.from_password("testuser", SecretValue.unsafe_plain_text("password1234!")),
        # add default database name Population
        default_database_name = "Population",
        instance_props={
            "vpc": vpc,
            "security_groups": [rds_sg],
            "vpc_subnets": ec2.SubnetSelection(subnet_type = ec2.SubnetType.PRIVATE_ISOLATED)
        },
        instances = 1
        )

# define an Amazon Linux 2023 image
ami = ec2.MachineImage.latest_amazon_linux2023()

# read userdata.sh file from cdkapp directory using readlines
with open("cdkapp/userdata.sh", "r") as f:
    userdata = f.readlines()

# Add each line from the script to ec2 UserData
ec2_user_data = ec2.UserData.for_linux()
for line in userdata:
    ec2_user_data.add_commands(line.strip())

create a t3.small ec2 instance for the web server in a private egress subnet and vpc.availability_zones[0]

ec2_instance = ec2.Instance(self, "MyInstance",
        instance_type = ec2.InstanceType("t3.small"),
        machine_image = amzn_linux,
        vpc = vpc,
        vpc_subnets = ec2.SubnetSelection(subnet_type = ec2.SubnetType.PRIVATE_WITH_EGRESS),
        availability_zone = vpc.availability_zones[0],
        user_data = user_data,
        security_group = ec2_sg,
        # add an existing role with name ec2_instance_role
        role = iam.Role.from_role_name(self, "ec2_instance_role", "ec2_instance_role")
)
    

# add depends
ec2_instance.node.add_dependency(cluster)

# create a load balancer in the public subnet
alb = elbv2.ApplicationLoadBalancer(
    self,
    "ALB",
    vpc=vpc,
    internet_facing=True,
    security_group=alb_sg
)

# add a listener on port 80 to the load balancer with open=True
listener = alb.add_listener("Listener", port=80, open=True)

# add targets to the load balancer using port 80 with unhealthy healthcheck threshold count 5

listener.add_targets("Target", port=80, targets=[ec2_instance], health_check=elbv2.HealthCheck(
    enabled=True,
    healthy_threshold_count=5,
    interval=Duration.seconds(60),
    path="/",
    timeout=Duration.seconds(10),
    unhealthy_threshold_count=2
))   

# add depends on for the listener to wait for the ec2 instance
listener.node.add_dependency(ec2_instance)