fact: Definition functor_preserves_retraction {a b : C} (H : retraction b a) : retraction (F b) (F a) := _ ,, _ ,, functor_preserves_is_retraction H.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Functors