private function transformRow(&$row)
    {
        // Check modify for any specific key manipulations.
        if (array_has($this->config, 'modify')) {
            foreach ($row as $key => &$value) {
                if (array_has($this->config['modify'], $key)) {
                    $this->config['modify'][$key]($value, $row);
                }
                unset($value);
            }
        }
    }