[yt-dev] Boolean data objects in yt-3

Hi folks, I've stumbled across across a research task that could really use yt's Boolean data object feature, and according to the documentation it is not implemented in yt-3. Have boolean data objects been replaced by something else? I know there are various filtering methods in yt, but what I really need to do is spatial filtering (i.e., data in a sphere with some chunks of the sphere excised). In principle I'd be happy to take a crack at re-implementing it, although I might need some help. Could somebody give me a sense of why it wasn't ported to yt-3 when the changeover was made? Thanks, Brian