protected function select($columns = null, $where = null, $size = null, $offset = null)
    {
        if (!$columns) {
            $columns = '*';
        }
        if (!is_array($columns)) {
            $columns = [$columns];
        }

        $query = 'SELECT ' . implode(',', $columns) . ' FROM ' . self::DIAGNOSTIC_TABLE;

        return $this->query($query, $where, $size, $offset);
    }