When an event is a visibility change event, as per MSC3531, the visibility change implied by the event.
The event id affected.
Optionally, a human-readable reason explaining why the event was hidden. Ignored if the event was made visible.
If true, the target event should be made visible. Otherwise, it should be hidden.
true
When an event is a visibility change event, as per MSC3531, the visibility change implied by the event.