∀ {α : Type u} {β : α → Type v} [inst : Ord α] {t : Std.DTreeMap.Internal.Impl α β} {k : α} [inst_1 : Inhabited α],
  Std.DTreeMap.Internal.Impl.getKeyLT! k t = (Std.DTreeMap.Internal.Impl.getKeyLT? k t).get!