proposition: Lemma fsubsetIr A B : A `&` B `<=` B.
proof: Proof. by apply/fsubsetP=> x; rewrite inE => /andP []. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)