proposition: Theorem finite_t_option X : finite_t X -> finite_t (option X).
proof: Proof. intros (lX & HX). exists (None :: map Some lX). intros [x|]; simpl; auto. right; apply in_map_iff; exists x; auto. Qed.
imports: List Arith Lia Eqdep_dec Bool Undecidability.Shared.Libs.DLW.Utils(utils_tac utils_list utils_nat) Undecidability.Shared.Libs.DLW.Vec(pos vec)