fact: Definition disp_functor_ff_disp_functor_id {C : category} (D : disp_cat C) : disp_functor_ff (disp_functor_identity D).
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Prelude UniMath.CategoryTheory.DisplayedCats.Core UniMath.CategoryTheory.DisplayedCats.Isos UniMath.CategoryTheory.DisplayedCats.Functors