public function get_shared(string $id): ?array
  {
    if ( bbn\str::is_uid($id) ){
      return $this->db->rselect_all($this->class_table, [
        $this->fields['id'],
        $this->fields['id_user'],
        $this->fields['id_group']
      ], [
        $this->fields['id_alias'] => $id
      ]);
    }
    return null;
  }