fact: Definition isequiv_sigma_category_isomorphism {s d : category F} : (s <~=~> d)%category <~> { e : (s.(c) <~=~> d.(c))%category | (F _1 e s.(x) = d.(x))%category }.
imports: Category.Core Functor.Core Category.Morphisms SetCategory.Core Grothendieck.ToSet.Core HoTT.Basics HoTT.Types