fact: Definition isaprop_internal_sfib (HB_2_1 : is_univalent_2_1 B) : isaprop internal_sfib.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Isos UniMath.CategoryTheory.DisplayedCats.StreetFibration UniMath.Bicategories.Core.Bicat UniMath.Bicategories.Core.Invertible_2cells UniMath.Bicategories.Core.Univalence