proposition: Lemma Empty_set_spec: forall A (v: A), Empty_set A v <-> False.
proof: Proof. intros. split; intros []. Qed.
imports: Coq.Classes.Morphisms Coq.Classes.Equivalence Coq.Sets.Ensembles Coq.Sets.Constructive_sets CertiGraph.lib.Coqlib CertiGraph.lib.EquivDec_ext