Error to Server::getScheduler

I have an error in my code that I can not solve:

HTML:

[Server thread/CRITICAL]: Error: "Call to undefined method pocketmine\Server::getScheduler()" (EXCEPTION) in "GunCore v17/src/GunCore/Main" at line 108[m

Code :

PHP:

    $this->getServer()->getScheduler()->scheduleRepeatingTask(new ClearLaggTask($this), 12000);

 

Replace with:
$this->getServer()->getScheduler()->scheduleRepeatingTask(new ClearLaggTask($this), 12000);
Change PluginTask to Task on the ClearLaggTask file.
And on its constructor, remove parent::__construct(...);

 

Move to facepalm?

 

As far as I know, the getServer() function is completely obsolete for normal (not Async) tasks now since all plugins have their own sheduler, so shouldn't it be

PHP:

$this->getScheduler()->scheduleRepeatingTask(new ClearLaggTask($this), 12000);


?