proposition: Lemma nbhs_subspace_filter (x : subspace A) : ProperFilter (nbhs_subspace x).
proof: Proof. case: nbhs_subspaceP_subproof => ?; last exact: globally_properfilter. by apply: within_nbhs_proper; apply: subset_closure. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed