proposition: Lemma actperm_id p : actperm perm_action p = p.
proof: Proof. by apply/permP=> x; rewrite permE. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)