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