fact: Definition step_list (pg : PreGraph) n l : Prop := forall n', In n' l <-> step pg n n'.
imports: Coq.Logic.ProofIrrelevance CertiGraph.lib.Ensembles_ext CertiGraph.lib.EquivDec_ext CertiGraph.lib.List_ext CertiGraph.lib.relation_list CertiGraph.lib.Equivalence_ext