proposition: Lemma numE_pos: forall g, 0 <= numE g.
proof: Proof. intros. unfold numE. apply Zlength_nonneg. Qed.
imports: VST.floyd.proofauto CertiGraph.lib.Coqlib CertiGraph.lib.EquivDec_ext CertiGraph.lib.List_ext CertiGraph.graph.graph_model CertiGraph.graph.graph_gen CertiGraph.graph.FiniteGraph CertiGraph.graph.undirected_graph