Getting json failure message while trying to edit the pyStages view.

Scneario:

We are running a job schedular and updating case with some property in backend. In the mean time if some has opened the case, we want them to notify with refresh message to see the updates on case( Similar to refresh outdated list views)

To achive above scenario i am trying to add the banner widget in pyStage and to update conditionally to display message.

Note: Not looking for custom DX component.