use TYPO3\HtmlSanitizer\Behavior;
use TYPO3\HtmlSanitizer\Builder\Preset\IframePreset;
$behavior = (new Behavior())
->withFlags(Behavior::ENCODE_INVALID_TAG | Behavior::REMOVE_UNEXPECTED_CHILDREN)
->withName('scenario-test')
->withPreset(new IframePreset());