proposition: Lemma openE_subproof : open_of_nbhs = [set A : set T | A `<=` nbhs^~ 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