proposition: Lemma g2_A11 (F: graph2): F·top ≃2 dom F·top.
proof: Proof. irewrite topR. symmetry. by irewrite topR. Qed.
imports: HB(structures) Coq(Setoid Morphisms) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij equiv) GraphTheory(setoid_bigop structures pttdom mgraph ptt)