protected function filterRow(RowInterface $row): RowInterface
    {
        if (empty($this->getFields())) {
            return $row;
        }
        $fields = array_keys($row->toArray());
        $toDelete = array_diff($fields, $this->getFields());

        foreach ($toDelete as $field) {
            unset($row->$field);
        }
        return $row;
    }