proposition: Lemma nbhs_subspaceP (x : subspace A) : nbhs_subspace_spec x (A x) (~ A x) (x \in A) (nbhs x).
proof: Proof. exact: nbhs_subspaceP_subproof. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed