proposition: Lemma decE (e : edge G) : (e \in edge_set C) + (e \in edge_set (~: C)).
proof: Proof. exact: edge_comp. Qed.
imports: Coq(Setoid Morphisms) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient bij preliminaries) GraphTheory(digraph sgraph treewidth minor checkpoint) GraphTheory(setoid_bigop structures mgraph mgraph2)