fact: Definition maybe_choice' {X : UU} (e : maybe X) : coprod (∑ x:X, e = just x) (e = nothing).
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Combinatorics.Maybe UniMath.Combinatorics.StandardFiniteSets UniMath.Algebra.Domains_and_Fields UniMath.Algebra.RigsAndRings