Error creating http event with cognito user pool authorizer

Hi, Newbie here,

I’m configuring a serverless typescript service using the aws-nodejs-typescript boilerplate. The documentation shows that you can create a cognito userpool as a resource and supply that as the authorizer for a function.

Docs:

functions:
  create:
    handler: posts.create
    events:
      - http:
          path: posts/create
          method: post
          integration: lambda
          authorizer:
            name: MyAuthorizer
            type: COGNITO_USER_POOLS
            arn:
              Fn::GetAtt:
                - CognitoUserPool
                - Arn
---
resources:
  Resources:
    CognitoUserPool:
      Type: 'AWS::Cognito::UserPool'
      Properties: ...

My typescript:

functions: {    
    create_admin_user : {
        handler: '/handler.adminIndex',
        events : [
          {
            http : {
              method: 'post',
              path: 'user/admin',
              cors : true,
              authorizer :{
                name : "MyCognitoUserPool",
                type: 'COGNITO_USER_POOLS',
                arn: {"Fn::GetAtt" : ["CognitoUserPool","Arn"]}
              }
            }
  
          }
        ]
    }
},
resources: {
    Resources : {
      CognitoUserPool: {
        Type: "AWS::Cognito::UserPool",
         Properties : ....
      }
    }
}

In the IDE (VSCode) I get an error: Type ‘{ “Fn::GetAtt”: string[]; }’ is not assignable to type ‘string’.

And thus it fails to deploy. Can anyone provide some insight. I’ve seen forums where this is the accepted solution. Is this a typescript issue? And if so, can anyone suggest a suitable workaround?