∀ {α : Type u} {cmp : α → α → Ordering} {β : Type v} [inst : Std.TransCmp cmp] [inst_1 : Inhabited β]
  (t t_1 : Std.ExtDTreeMap α (fun x => β) cmp),
  t = t_1 → ∀ (a a_1 : α), a = a_1 → Std.ExtDTreeMap.Const.get! t a = Std.ExtDTreeMap.Const.get! t_1 a_1