[nova] How to use $aggregates with JsonFilter

Hey Team, I'm trying to use scheduler hints using the JsonFilter that involve host aggregates. Based on the documentation and my quick perusal of the scheduler's HostState class... it seems like $aggregates are populated there for usage, but I can't seem to find the right magick to make a json query work to schedule an instance on a host that belongs to a specific aggregate based on simply the name of the aggregate... or perhaps metadata contained within. I think my lack of understanding of the structure of the $aggregates list in the scheduler's HostState class is tripping me up. Does anyone have any insight into this?... Thanks. -- Andy Speagle