proposition: Fact fo_bisimilar_sym x y : x ≐ y -> y ≐ x.
proof: Proof. unfold fo_bisimilar; intros H ? ? ? ?; rewrite H; auto; tauto. Qed.
imports: List Arith Nat Lia Relations Bool Undecidability.Shared.Libs.DLW.Utils(utils_tac utils_list utils_nat finite) Undecidability.Shared.Libs.DLW.Vec(pos vec) Undecidability.FOL.TRAKHTENBROT(notations decidable gfp fol_ops fo_sig fo_terms fo_logic fo_definable fo_sat)