∀ {𝒮 : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} 𝒮]
  {F : CategoryTheory.Pseudofunctor (CategoryTheory.LocallyDiscrete 𝒮) CategoryTheory.Cat} {a b : F.Grothendieck}
  (f g : a ⟶ b),
  f = g ↔ ∃ (hfg : f.base = g.base), CategoryTheory.CategoryStruct.comp (CategoryTheory.eqToHom ⋯) f.fiber = g.fiber