fact: Definition predicate_sub_mathgraph (g: PreGraph V E) (p: V -> Prop) (MA: MathGraph g is_null): MathGraph (predicate_subgraph g p) is_null.
imports: CertiGraph.lib.Coqlib CertiGraph.lib.Ensembles_ext CertiGraph.lib.EquivDec_ext CertiGraph.lib.List_ext CertiGraph.lib.relation_list CertiGraph.lib.Equivalence_ext CertiGraph.graph.graph_model CertiGraph.graph.graph_gen