proposition: Lemma appfilter U V (f : U -> V) (F : set_system U) : f @ F = [set P : set _ | \forall x \near F, P (f x)].
proof: Proof. by []. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed