How to debug a Lambda function in Cloud9?

Question

How do I debug a Lambda function in Cloud9 ? I tried to debug a file with a lambda and it started but lambda itself has not been invoked. What is the proper way to do this?

This is screen of function based on SAM init hello world application.

This is definition of resource from template.yaml:

Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function # More info about Function Resource: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#awsserverlessfunction
    Properties:
      CodeUri: hello_world/
      Handler: app.lambda_handler
      Runtime: python3.7
      Events:
        HelloWorld:
          Type: Api # More info about API Event Source: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#api
          Properties:
            Path: /hello
            Method: get