Why AWS SDK causing Jest Open Handle error?

I'm using jest for my backend testing. Here I'm login to aws using aws-sdk. I get the response successfully, then complete the test case, but then jest throws an error about open handles.

const login = (options) => {
    const cognito = new aws_sdk.CognitoIdentityServiceProvider();
    const request = cognito.initiateAuth({
        "AuthParameters": {
            "USERNAME": options.username,
            "PASSWORD": options.password,
        },
        "ClientId": options.CLIENT_ID
    });

    return request;
};

After searching, I found people have this error when connecting with database, and not closing database connect / their nodejs server. These issue is not with my application as I'm my backend is completely serverless.I is not an express app.