proposition: Lemma map_mx_repr : mx_repr G (map_repr_mx f rG).
proof: Proof. split=> [|x y Gx Gy]; first by rewrite /map_repr_mx repr_mx1 map_mx1. by rewrite -map_mxM -repr_mxM. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div choice fintype tuple finfun bigop prime) mathcomp(ssralg poly polydiv finset fingroup morphism) mathcomp(perm automorphism quotient finalg action zmodp) mathcomp(commutator cyclic center pgroup matrix mxalgebra) mathcomp(mxpoly)