code: public function getDomainCacheRuleTasks($domain, $ruleId)
      {
          return json_decode(self::getClient()->getDomainCacheRuleTasks($this->sn, $domain, $ruleId));
      }
docs: Return array of taskId associated with rule $ruleId of domain $domain
  
  @param string $domain
  @param int $ruleId
  @return array of task id (int)