Effect(PMMP 4.0.0)

What is wrong?

Error: "Call to undefined method pocketmine\entity\effect\Effect::getEffect()" (EXCEPTION) in "plugins/Borrow_plugin/src/Borrow/MainBorrow" at line 34

<?php

namespace Borrow;

use pocketmine\plugin\PluginBase;
use pocketmine\event\Listener;
use pocketmine\event\entity\EntityDamageEvent;
use pocketmine\event\entity\EntityDamageByEntityEvent;
use pocketmine\event\entity\EntityDamageByChildEntityEvent;
use pocketmine\entity\effect\Effect;
use pocketmine\entity\Entity;
use pocketmine\utils\Config;
use pocketmine\inventory\Inventory;
use pocketmine\entity\EffectInstance;
use pocketmine\player\Player;

class MainBorrow extends PluginBase implements Listener {

function onEnable() : void {
$this->config = new Config($this->getDataFolder()."config.yml", Config::YAML);
$this->getServer()->getPluginManager()->registerEvents($this, $this);
$this->getLogger()->info("lol");
}

function onDisable() : void {
$this->getLogger()->info("lol");
}

public function onDamage(EntityDamageEvent $event){
if($event instanceof EntityDamageByEntityEvent && $event->getDamager() instanceof Player) {
$player = $event->getEntity();
$damager = $event->getDamager();
if($damager->getInventory()->getItemInHand()->getId() == 261){
$effect = Effect::getEffect(9);
$effect = new EffectInstance($effect, 20 * 5, 1);
$entity->addEffect($effect);
}
}
}
}

 

PHP:

use pocketmine\entity\Living;
use pocketmine\entity\effect\{Effect, EffectInstance, VanillaEffects};
use pocketmine\event\entity\{EntityDamageByEntityEvent, EntityDamageEvent};
use pocketmine\item\VanillaItems;
use pocketmine\player\Player;


PHP:

public function onDamage(EntityDamageEvent $event): void {
    if ($event instanceof EntityDamageByEntityEvent && ($damager = $event->getDamager()) instanceof Player) {
        $entity = $event->getEntity();
        if ($entity instanceof Living && $damager->getInventory()->getItemInHand()->equals(VanillaItems::BOW(), false, false)) {
            $entity->getEffects()->add(new EffectInstance(VanillaEffects::NAUSEA(), 20 * 5, 1));
        }
    }
}