fact: Definition K_0_map {M N:ExactCategory} (F:ExactFunctor M N) : monoidfun (K_0 M) (K_0 N).
imports: UniMath.Tactics.EnsureStructuredProofs UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.ExactCategories.ExactCategories UniMath.Algebra.Groups UniMath.Algebra.Free_Monoids_and_Groups