proposition: Lemma nbhsE_subproof (p : T) : nbhs p = [set A | exists B, [/\ op B, B p & B `<=` A] ].
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