Invoke untyped activities asynchronously

I am referring this doc Java SDK developer's guide - Foundations | Temporal Documentation
We are looking at invoking untyped or dynamic activities asynchronously. The example given in the documentation only covers Async invocation using method reference. Please provide an example for untyped or dynamic activies

Promise<String> localNamePromise = Async.function(activities::download, sourceBucket, sourceFile);

Found a way soon after filing query here