∀ {α : Type u} {β : α → Type v} {cmp : α → α → Ordering} [inst : Std.LawfulEqCmp cmp] [inst_1 : Std.TransCmp cmp]
  [inst_2 : (k : α) → BEq (β k)] [∀ (k : α), LawfulBEq (β k)], LawfulBEq (Std.ExtDTreeMap α β cmp)