∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] (G : CategoryTheory.Functor C (Type w))
  (X : CategoryTheory.Grothendieck (G.comp CategoryTheory.typeToCat)),
  ((CategoryTheory.Grothendieck.grothendieckTypeToCat G).unitIso.inv.app X).fiber = CategoryTheory.eqToHom ⋯