AWS CDK Python调用ALB metric_http_code_elb报AttributeError

Python环境下使用AWS CDK开发，引用已有ALB资源并调用其metric_http_code_elb方法时，抛出如下属性错误：

AttributeError: '<class 'aws_cdk.Resource'>+<class 'aws_cdk.aws_elasticloadbalancingv2._IApplicationLoadBalancerProxy'>' object has no attribute 'metric_http_code_elb'.

load_balancer = elbv2.ApplicationLoadBalancer.from_lookup(
    self,
    "ALB",
    load_balancer_arn="arn:aws:elasticloadbalancing:ap-south-1:345396902820:loadbalancer/app/QA-Env-Public-ALB/573f88222ed64875"
)        
http_5xx_metric = load_balancer.metric_http_code_elb()

• from_lookup方法返回的是IApplicationLoadBalancer接口的代理对象，不是ApplicationLoadBalancer实体类实例
• metric_http_code_elb这类指标便捷构造方法，仅在ALB实体类上实现，接口代理类未定义对应方法，直接调用就会触发属性不存在的报错

放弃调用实例自带的指标方法，手动构造CloudWatch指标对象即可，效果和内置方法完全一致，参考实现：

from aws_cdk import Duration
from aws_cdk import aws_cloudwatch as cw

load_balancer = elbv2.ApplicationLoadBalancer.from_lookup(
    self,
    "ALB",
    load_balancer_arn="arn:aws:elasticloadbalancing:ap-south-1:345396902820:loadbalancer/app/QA-Env-Public-ALB/573f88222ed64875"
)

http_5xx_metric = cw.Metric(
    namespace="AWS/ApplicationELB",
    metric_name="HTTPCode_ELB_5XX_Count",
    dimensions_map={
        "LoadBalancer": load_balancer.load_balancer_full_name
    },
    period=Duration.minutes(1),
    statistic="Sum"
)

提示：其他ALB相关指标（包括目标组维度、监听器维度的指标）都可以通过该方式手动构造，只需要对应调整指标名、维度参数即可。

内容的提问来源于stack exchange，提问作者shikha singh