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

    public function getChildren($name)
    {
        $query = (new Query())->from($this->itemCollection)->where(['parents' => ['$in' => [$name]]]);
        $children = [];
        foreach ($query->all($this->db) as $row) {
            $children[$row['name']] = $this->populateItem($row);
        }
        return $children;
    }