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

    public function getRolesByUser($userId)
    {
        if (!isset($userId) || $userId === '') {
            return [];
        }
        $rows = (new Query())->select(['item_name'])->from($this->assignmentCollection)->where(['user_id' => (string) $userId])->all($this->db);
        if (empty($rows)) {
            return [];
        }
        $itemNames = ArrayHelper::getColumn($rows, 'item_name');
        $query = (new Query())->from($this->itemCollection)->where(['name' => $itemNames])->andWhere(['type' => Item::TYPE_ROLE]);
        $roles = [];
        foreach ($query->all($this->db) as $row) {
            $roles[$row['name']] = $this->populateItem($row);
        }
        return $roles;
    }