fact: Definition length_of_zig_zag {C : category} {x y : C} (gs : zig_zag x y) : ℕ := pr1 gs.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Isos UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.Groupoids