fact: Definition in_edges (pg : PreGraph) x: Ensemble Edge := fun e => evalid pg e /\ dst pg e = x.
imports: Coq.Logic.ProofIrrelevance CertiGraph.lib.Ensembles_ext CertiGraph.lib.EquivDec_ext CertiGraph.lib.List_ext CertiGraph.lib.relation_list CertiGraph.lib.Equivalence_ext