get Overlapping Signature Async
Searches the document for an ink or stamp signature that overlaps this form element, asynchronously.
- Scheduler:
- This method operates on background Scheduler.
Return
An instance of Maybe that either emits the overlapping Annotation in `onSuccess()` or terminates with `onCompleted()` or `onError()`. The Annotation can be an InkAnnotation or StampAnnotation.