proposition: Lemma fsetIidPr {A B} : reflect (A `&` B = B) (B `<=` A).
proof: Proof. by rewrite fsetIC; apply: fsetIidPl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)