proposition: Lemma fdisjoint_sym A B : [disjoint A & B] = [disjoint B & A].
proof: Proof. by rewrite -!fsetI_eq0 fsetIC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)