proposition: Lemma injm_pcore pi G : G \subset D -> f @* 'O_pi(G) = 'O_pi(f @* G).
proof: Proof. exact: injmF. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(fintype bigop finset prime fingroup morphism) mathcomp(gfunctor automorphism quotient action gproduct) mathcomp(cyclic)