proposition: Lemma sub_symconnect_to (a b : pred V) : a \subset b -> subrel (symconnect_to a) (symconnect_to b).
proof: Proof. by move=> subab ?? /andP[??]; rewrite /symconnect !(sub_connect_to subab). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice fintype tuple) mathcomp(bigop finset finfun perm fingraph path div) bigmin