proposition: Lemma braid_equiv : equivalence_rel braidcongr.
proof: Proof. Proof using. by apply: gencongr_equiv; exact: braidrule_sym. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(fingroup perm morphism presentation) mathcomp(ssralg poly ssrint) permcomp tools permuted combclass congr