proposition: Proposition double_id_mor_id {C : category} {D : twosided_disp_cat C C} (I : hor_id D) (x : C) : double_id_mor I (identity x) = id_two_disp _.
proof: Proof. exact (pr12 I x). Defined.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Isos UniMath.CategoryTheory.TwoSidedDisplayedCats.TwoSidedDispCat UniMath.CategoryTheory.TwoSidedDisplayedCats.Isos