1. `filters` == [`request.GET` data](https://github.com/chuckharmston/zamboni/blob/62b213c213b33fd3a6df62efe1a6950819f9b2ec/mkt/search/api.py#L145) (which should contain `region` and `carrier`)
1. `filters` passed to [`CollectionFilterSetWithFallback`](https://github.com/chuckharmston/zamboni/blob/62b213c213b33fd3a6df62efe1a6950819f9b2ec/mkt/search/api.py#L150)
1. `CollectionFilterSetWithFallback` has `carrier` and `region` as [filter fields](https://github.com/chuckharmston/zamboni/blob/62b213c2/mkt/collections/filters.py#L47-50)