DB connection to the AWS istance

Question

I need to set up PostgreSQL db connection for AWS instance. First i need to create a tunnel to the instance. I can do this with AWS CLI and session manager, by running:

aws ssm start-session --target <instanceID> --document-name AWS- StartPortForwardingSessionToRemoteHost --parameters '{"host":["host"], "portNumber":["5432"], "localPortNumber":["5432"]}'

But when I trying to do this in Robot test using boto3 library:

@keyword(name="AWS Start Tunnel")
    def start_tunnel(self, instanceID: str) -> str:
        ssm_client = boto3.client('ssm')
        response = ssm_client.start_session(
            Target=instanceID,
            DocumentName='AWS-StartPortForwardingSessionToRemoteHost',
            Reason='Robot Test',
            Parameters={'host': ['host'], 
                'portNumber': ['5432'],
                'localPortNumber': ['5432']} 
            )      
        return response

It is creates the session but looks like not connected to it, because I cannot connect to the db. Maybe I need to have a webSocket connection also?

AWS CLI is works. test with boto3 - not.