proposition: Lemma fsub0 A : fsub A fset0 = set0 :> {set A}.
proof: Proof. by apply/setP => x; rewrite !inE. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)