∀ {α : Type u_1} {m : Type u_1 → Type u_2} {β : Type u_1} [inst : Monad m] [Std.Iterator α m β] {it : Std.IterM m β}
  {P : β → Bool}, Std.IterM.dropWhile P it = Std.IterM.Intermediate.dropWhile P true it