public function getAddonsForPlan(array $plans, string $addonType = null): array
    {
        $addonApi = new Addon($this->token, $this->organizationId, $this->cache, $this->ttl);

        foreach ($plans as &$plan) {
            $addons = [];

            foreach ($plan['addons'] as $planAddon) {
                $addon = $addonApi->getAddon($planAddon['addon_code']);

                if (null !== $addonType) {
                    if (($addon['type'] == $addonType) && (in_array($addonType, self::$addonTypes))) {
                        $addons[] = $addon;
                    }
                } else {
                    $addons[] = $addon;
                }
            }

            $plan['addons'] = $addons;
        }

        return $plans;
    }