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