proposition: Lemma edge_set1 x : edge_set [set x] = edges x x.
proof: Proof. apply/setP=> e. by rewrite !inE. Qed.
imports: Coq(Morphisms RelationClasses) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij) GraphTheory(equiv digraph setoid_bigop structures)