gistfile1.txt

$step = $this;
$callback = function(\TYPO3\Form\Core\Model\FinisherContext $finisherContext) use ($step) {
    $step->importSite($finisherContext);
};
$this->closureFinisher = new \TYPO3\Form\Finishers\ClosureFinisher();
$this->closureFinisher->setOption('closure', $callback);