在Cloudformation模板中，如何在IoT规则中引用动态生成的Lambda函数ARN？

Resources:
  MyLambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: MyLambdaFunction
      Runtime: nodejs14.x
      Handler: index.handler
      Code:
        ZipFile: |
          exports.handler = async (event) => {
            console.log('Hello from Lambda!');
          }

  MyTopicRule:
    Type: AWS::IoT::TopicRule
    Properties:
      RuleName: MyTopicRule
      TopicRulePayload:
        Sql: "SELECT * FROM 'my/topic'"
        Actions:
          - Lambda:
              FunctionArn: !GetAtt MyLambdaFunction.Arn