yii\mongodb\rbac\MongoDbManager::removeChildren PHP Method

    public function removeChildren($parent)
    {
        $result = $this->db->getCollection($this->itemCollection)->update([], ['$pull' => ['parents' => ['$in' => [$parent->name]]]], ['multi' => true]) > 0;
        $this->invalidateCache();
        return $result;
    }