private function getLimitationTypes()
    {
        $limitationTypes = [];
        foreach ($this->policyMap as $module) {
            foreach ($module as $policy) {
                if (null === $policy) {
                    continue;
                }

                foreach (array_keys($policy) as $limitationType) {
                    if (!in_array($limitationType, $limitationTypes)) {
                        $limitationTypes[] = $limitationType;
                    }
                }
            }
        }

        return $limitationTypes;
    }