FluidTYPO3\Vhs\ViewHelpers\Media\ExistsViewHelper::initializeArguments PHP Method

    public function initializeArguments()
    {
        parent::initializeArguments();
        $this->registerArgument('file', 'string', 'Filename which must exist to trigger f:then rendering');
        $this->registerArgument('directory', 'string', 'Directory which must exist to trigger f:then rendering');
    }