∀ {α : Type u} {β : α → Type v} [inst : Ord α] [inst_1 : Std.TransOrd α] {t : Std.DTreeMap.Internal.Impl α β} {k : α}
  {hto : t.Ordered} {he : ∃ a ∈ t, compare a k = Ordering.gt},
  Std.DTreeMap.Internal.Impl.getKeyGT k t hto he = (Std.DTreeMap.Internal.Impl.getEntryGT k t hto he).fst