proposition: Lemma ostepL G G' H : ostep G G' -> osteps G' H -> osteps G H.
proof: Proof. move => A. apply: osteps_trans. exact: ostep_step. 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)