pocketmine\scheduler\TaskHandler::cancel PHP Method

    public function cancel()
    {
        if (!$this->isCancelled()) {
            $this->task->onCancel();
        }
        $this->remove();
    }

 public function setUpdateInterval($interval)
 {
     $this->handler->cancel();
     $this->handler = $this->getOwner()->getServer()->getScheduler()->scheduleRepeatingTask($this, $interval);
 }