proposition: Lemma openT : open (setT : set T).
proof: Proof. by rewrite openE => ??; apply: filterT. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed