Backend\Modules\Extensions\Actions\ExportThemeTemplates::getContent PHP Method

    public function getContent()
    {
        $filename = 'templates_' . BackendModel::getUTCDate('d-m-Y') . '.xml';
        return new Response(Model::createTemplateXmlForExport($this->selectedTheme), Response::HTTP_OK, ['Content-type' => 'text/xml', 'Content-disposition' => 'attachment; filename="' . $filename . '"']);
    }