∀ {α : Type u} [inst : Std.PRange.UpwardEnumerable α] [inst_1 : LT α] [inst_2 : DecidableLT α]
  [Std.PRange.LawfulUpwardEnumerable α] [Std.PRange.LawfulUpwardEnumerableLT α] {it : Std.Iter α} {out : α},
  it.IsPlausibleIndirectOutput out ↔
    ∃ n, (it.internalState.next.bind fun x => Std.PRange.succMany? n x) = some out ∧ out < it.internalState.upperBound