proposition: Lemma fsetKIidC A B : A `&` (B `&` A) = B `&` A.
proof: Proof. by rewrite fsetICA fsetIid. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)