can you show me where we pass the region & carrier to get the featured apps and operator shelf for that combination?

I can't [find](https://github.com/chuckharmston/zamboni/blob/62b213c/mkt/search/api.py#L147) [it](https://github.com/chuckharmston/zamboni/blob/62b213c2/mkt/collections/filters.py#L44)