∀ {α : Type u} {β : Type v} {cmp : α → α → Ordering} {δ : Type w} {m : Type w → Type w₂} [inst : Monad m]
  [inst_1 : LawfulMonad m] [inst_2 : Std.TransCmp cmp] (f f_1 : α → β → δ → m (ForInStep δ)),
  f = f_1 →
    ∀ (init init_1 : δ),
      init = init_1 →
        ∀ (t t_1 : Std.ExtTreeMap α β cmp),
          t = t_1 → Std.ExtTreeMap.forIn f init t = Std.ExtTreeMap.forIn f_1 init_1 t_1