CREATE_FAILED: ApiGatewayMethodActionPost (AWS::ApiGateway::Method) - Invalid type for parameter selectionPattern

I'm trying to deploy my serverless app on local stack but Invalid type parameter for selectionPattern error is being thrown. Below is the complete error and serverless.yml

Error:

ApiGatewayMethodActionPost (Parameter validation failed:; Invalid type for parameter selectionPattern, value: 200, type: <class 'int'>, valid types: <class 'str'>)

serverless.yml

  events:
    - http:
        path: /action
        method: POST
        iamRole: arn:aws:iam::xxxxxxxxxxxx:role/someRole
        action: StartSyncExecution
        request:
          template:
            application/json: |
              {
                "stateMachineArn":"arn:aws:states:'us-west-2':xxxxxxxxxxxx:stateMachine:someMachine",
                "input": "$util.escapeJavaScript($input.json('$'))"
              }
        response:
            template: 
              application/json: |
                $input.path('$.output')

I was checking serverless-step-function code where selectionPattern is defined as integer and not string. Following is the link to the code: code

Start with the serverless.yml configuration in the report and compare it with the linked serverless-step-functions lib/deploy/events/apiGateway/methods.js code at line 199. Reproduce the deployment against LocalStack, trace how selectionPattern is generated, and confirm the fix by verifying that the API Gateway method deploys without the parameter type error.