import public Data.Maybe
import public Data.SomaybeSo : (b : Bool) -> Maybe (So b)Try and convert a boolean to `So`, that is, a proof that the
boolean in question equals `True`.
refineSo : {f : a -> Bool} -> ((v : a) -> (0 _ : So (f v)) -> b) -> a -> Maybe bTry to create a refined value that requires an erased proof of `So (f v)`.