Hey! Sorry for the late reply. Just notice it.
No, it isn’t possible. Facets aren’t first-class citizen.
Instead of using the Upsert Procedure, why not Upsert Block instead? https://dgraph.io/docs/mutations/upsert-block/#sidebar
Continuing
Instead of using Facets to hold such important information. Rather than this, I would create a specific entity and set my Graph Model around it - it would be an intermediate node between the user and the object(the car). As this entity is a first-class citizen, now you could do anything you want.
Cheers.