fact: Definition double_id_mor_id_comp {C : category} {D : twosided_disp_cat C C} (I : hor_id D) {x y z : C} (f : x --> y) (g : y --> z) : double_id_mor I (f · g) = double_id_mor I f ;;2 double_id_mor I g.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Isos UniMath.CategoryTheory.TwoSidedDisplayedCats.TwoSidedDispCat UniMath.CategoryTheory.TwoSidedDisplayedCats.Isos