∀ {α : Type u_1} {cmp : α → α → Ordering} {β : Type u_2} [Std.TransCmp cmp] (t : Std.ExtDTreeMap α (fun x => β) cmp)
  (n : ℕ) (h : n < t.size) (x x_1 : Std.DTreeMap α (fun x => β) cmp) (x_2 : t = Std.ExtDTreeMap.mk x),
  t = Std.ExtDTreeMap.mk x_1 →
    ∀ (h_1 : x.Equiv x_1), Std.DTreeMap.Const.entryAtIdx x n ⋯ = Std.DTreeMap.Const.entryAtIdx x_1 n ⋯