∀ {α₁ β₁ : Type u_1} [inst : Std.Iterator α₁ Id β₁]
  (motive : Option { out // ∃ it, it.toIterM.IsPlausibleOutput out } → Sort u_2)
  (out₁ : { out // ∃ it, it.toIterM.IsPlausibleOutput out }) (h_1 : Unit → motive none)
  (h_2 : (out₁ : { out // ∃ it, it.toIterM.IsPlausibleOutput out }) → motive (some out₁)),
  (match some out₁ with
    | none => h_1 ()
    | some out₁ => h_2 out₁) =
    h_2 out₁