fact: Definition connected_by_path (g: PGraph) (p: upath) (n : V) := fun n' => valid_upath g p /\ hd_error p = Some n /\ last_error p = Some n'.
imports: Coq.Logic.Classical CertiGraph.lib.List_ext CertiGraph.lib.EquivDec_ext CertiGraph.graph.graph_model CertiGraph.graph.graph_relation CertiGraph.graph.path_lemmas CertiGraph.graph.graph_gen CertiGraph.graph.FiniteGraph