fact: Definition two_of_six {C : category} (W : morph_class C) := ∏ (x y z t : C) (f : x --> y) (g : y --> z) (h : z --> t) (gf : W x z (f · g)) (hg : W y t (g · h)), (W x y f) × (W y z g) × (W z t h) × (W x t (f · g · h)).
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Monics UniMath.CategoryTheory.Epis UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.Core.Isos