proposition: Lemma astabs_comp S : 'N(S | comp_action) = f @*^-1 'N(S | to).
proof: Proof. by apply/setP=> x; rewrite !inE -andbA. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)