proposition: Lemma classes_partition : partition (classes G) G.
proof: Proof. by apply: orbit_partition; apply/actsP=> x Gx y; apply: groupJr. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)