proposition: Lemma group_not0 G : set0 <> G.
proof: Proof. by move/setP/(_ 1); rewrite inE group1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(choice fintype bigop finset fingroup morphism) mathcomp(quotient action)