proposition: Lemma mx_nbhs_singleton M (A : set 'M[T]_(m, n)) : nbhs M A -> A M.
proof: Proof. by move=> [P M_P]; apply=> ??; apply: nbhs_singleton. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed