proposition: Proposition id_h_square_comp {C : double_cat} {x y z : C} (v₁ : x -->v y) (v₂ : y -->v z) : id_h_square (v₁ ·v v₂) = id_h_square v₁ ⋆v id_h_square v₂.
proof: Proof. apply double_id_mor_id_comp. Defined.
imports: UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.Core.NaturalTransformations UniMath.CategoryTheory.Core.Isos UniMath.CategoryTheory.TwoSidedDisplayedCats.TwoSidedDispCat UniMath.CategoryTheory.TwoSidedDisplayedCats.Isos UniMath.CategoryTheory.TwoSidedDisplayedCats.Univalence UniMath.Bicategories.Core.Examples.BicatOfUnivCats UniMath.Bicategories.DoubleCategories.Basics.DoubleCategoryBasics