public function delete($id)
 {
     $sheet_id = $this->available($id);
     $res = $this->deleteByField(array('id' => $id, 'sheet_id' => $sheet_id));
     $sheet = new stickiesSheetModel();
     $sheet->refresh($sheet_id, $this->countByField('sheet_id', $sheet_id));
     return $res;
 }