proposition: Lemma morphpre_maximal_eq : maximal_eq (f @*^-1 M) (f @*^-1 G) = maximal_eq M G.
proof: Proof. by rewrite /maximal_eq morphpre_maximal !eqEsubset !morphpreSK. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(fintype bigop finset fingroup morphism) mathcomp(automorphism quotient action commutator center)