proposition: Lemma cons_iso_steps G G' H : steps G' H -> G ≃2 G' -> steps G H.
proof: Proof. intros E F. etransitivity. apply iso_step, F. assumption. Qed.
imports: HB(structures) Coq(Setoid Morphisms) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij equiv) GraphTheory(setoid_bigop structures pttdom mgraph mgraph2 rewriting)