∀ {α : Type w} {m : Type w → Type w'} {β : Type w} {P : β → Prop} {n : Type u_1 → Type u_2} [inst : Std.Iterator α m β]
  [inst_1 : Monad m] [Monad n] {it : Std.IterM m β} {hP : ∀ (out : β), it.IsPlausibleIndirectOutput out → P out}
  [Std.Iterators.Finite α m] [LawfulMonad m],
  (fun x => Array.map Subtype.val x) <$> (it.attachWith P hP).toArray = it.toArray