{C : Type u} →
  [inst : CategoryTheory.Category.{v, u} C] →
    (P : CategoryTheory.Functor Cᵒᵖ (Type (max v u))) →
      {X : C} →
        (R : CategoryTheory.Presieve X) →
          CategoryTheory.Equalizer.FirstObj P R ≅ CategoryTheory.Presieve.FamilyOfElements P R