How to pull the parent in Yii Nested Set behavior?

Question

Yii

I tried this webnotes.by/docs/php/yii/derevo-kategoriy-v-yii-s-... I downloaded the extension from here: https://github.com/yiiext/nested-set-behavior id - shnik is not involved. Then 1. How to pull out the parent all the same? (I also tried $parent=$category->parent; - but as I understand it, the property was meant; Taken from here www.yiiframework.com/extension/nestedsetbehavior ) 2. What is meant by getRoot (which function is not in the behavior)
$root = Category::getRoot(new Category);