private function getColumns()
    {
        $class = new \ReflectionClass(__CLASS__);
        $constants = $class->getConstants();
        $columns = [];
        foreach ($constants as $constant => $value) {
            if (strpos($constant, 'DIAGNOSTIC_') === 0) {
                array_push($columns, $value);
            }
        }
        if (empty($columns)) {
            throw new StorageException('No column to fill into CSV storage');
        }
        return $columns;
    }