∀ {α : Type u_1} {β : Type u_2} {R : α → β → Prop} {l₁ : List α} {l₂ : List β},
  List.Forall₂ R l₁ l₂ ↔
    l₁.length = l₂.length ∧ ∀ (i : ℕ) (h₁ : i < l₁.length) (h₂ : i < l₂.length), R (l₁.get ⟨i, h₁⟩) (l₂.get ⟨i, h₂⟩)