Admitted. (* QuickChick update_same. *)

(* Specifications: *)
Theorem update_permute : forall v1 v2 x1 x2
(m : partial_map),
x2 <> x1 ->
(update (x1,v1) (update (x2,v2) m))
= (update (x2,v2) (update (x1,v1) m)).