fact: Definition id2_pb_2cell {p q : pb_cone} (φ : pb_1cell p q) : pb_2cell φ φ.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.Bicategories.Core.Bicat UniMath.Bicategories.Core.Invertible_2cells UniMath.Bicategories.Core.Univalence