public function __construct()
{
$this->addFilter('name', (new StringFilter())->addCallback([StringFilter::class, 'nonEmpty']))->addFilter('author', new IntFilter())->addFilter('preamble', new StringFilter())->addFilter('format', (new WhiteList('HTML', 'Markdown', 'Rich Text', 'RST'))->setDefault('Rich Text'))->addFilter('config', new ArrayFilter())->addFilter('items', new StringFilter());
}