fact: Definition subgraph (H G : graph) := exists hv he hd, @is_ihom H G hv he hd /\ injective hv /\ injective he.
imports: Coq(Morphisms RelationClasses) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij) GraphTheory(equiv digraph setoid_bigop structures)