proposition: Lemma par2top (F: graph2): F ∥ top ≃2 F.
proof: Proof. irewrite (merge_union_K_l (K:=g2_top) _ _ (k:=fun b => if b then input else output))=>/=; try by repeat case. apply merge2_nothing. by repeat constructor. repeat case; apply /eqquotP; eqv. Qed.
imports: HB(structures) Coq(Setoid Morphisms) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij equiv) GraphTheory(setoid_bigop structures pttdom mgraph ptt)