[Docs] clarify helper.Data for update

If I want to return properties after creation (`helper.Data.update({})`), what do I have to do when updating?

If an update does not change the returned properties, can I just not touch `helper.Data`? Or do I need to fetch the data from somewhere else and pass it in again?

If an update does change the returned properties, but not all of them, do I only need to pass the new ones to `helper.Data.update({})`?

Start by reading the existing helper.Data.update documentation and its update behavior in the repository. Check the three cases raised in the issue—unchanged properties, partially changed properties, and newly returned properties—then document the required usage and expected result.

Written by the indexing model from the issue text.