Are there any code samples which show how to use Linked Entities with Excel custom functions?

Question

I am trying to make an Excel add-in like the built-in one for Stocks.

I need to fetch the data from an external source and have it update. Ideally, the updates would automatically stream in (over websocket or grpc-web) but I could also implement such that it requires the user to press Refresh (this seems to be how Stocks works?)

I started with https://learn.microsoft.com/en-us/office/dev/add-ins/quickstarts/excel-quickstart-jquery?tabs=yeomangenerator.

I see a note about how Stocks works at https://github.com/OfficeDev/office-js-docs-pr/blob/main/docs/excel/excel-data-types-concepts.md#linked-entities but I cannot find further info/examples on how to implement this.