proposition: Lemma iso_isubgraph (F G : sgraph) (i : F ≃ G) : F ⇀ G.
proof: Proof. exists i. exact: bij_injective. exact: edge_diso. Defined.
imports: Coq(Setoid CMorphisms) mathcomp(all_ssreflect) GraphTheory(edone preliminaries bij digraph) GraphTheory(set_tac)