proposition: Lemma nbhs_filter (p : T) : Filter (nbhs p).
proof: Proof. exact: (@nbhs_pfilter). Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed