proposition: Lemma principal_filter_proper {X} (x : X) : ProperFilter (principal_filter x).
proof: Proof. exact: globally_properfilter. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed