That's a fair question. Once this series of PRs is done I'd *certainly* like to have resolved it. But the contents and code locations are still somewhat in flux so I left it dangling! (For example, I'm working on some changes right now that introduce a new "mask" entry.) If you don't mind the chance of it moving again in the near future then I'm happy to shift it now. For what it's worth, I'm talking myself into wanting to move it now anyway (into `iris.analysis._interpolator`).