proposition: Lemma oarc_uniqeR e e' x y u : edges_at G y = [fset e] -> oarc G e' x u y -> e' = e.
proof: Proof. move => Iy /oarc_edge_atR. rewrite Iy. by move/fset1P. Qed.
imports: HB(structures) Coq(Relation_Definitions Morphisms RelationClasses) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij equiv) GraphTheory(setoid_bigop structures pttdom rewriting) GraphTheory(finmap_plus)