code: public function setBacklog(int $backlog): void
      {
          if ($this->client->call('recur.update', $this->jid, 'backlog', $backlog)) {
              $this->backlog = $backlog;
          }
      }
docs: Sets Job's backlog.
  
  @param  int $backlog
  @return void
  
  @throws QlessException
  @throws RuntimeException