fact: Definition adjacent_err g (u: option V) (v: option V) := match u, v with | None, None => True | None, Some v' => vvalid g v' | Some u', None => vvalid g u' | Some u', Some v' => adjacent g u' v' end.
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