pocketmine\event\HandlerList::getRegisteredListeners PHP Method

    public function getRegisteredListeners($plugin = null)
    {
        if ($plugin !== null) {
            $listeners = [];
            foreach ($this->getRegisteredListeners(null) as $hash => $listener) {
                if ($listener->getPlugin() === $plugin) {
                    $listeners[$hash] = $plugin;
                }
            }
            return $listeners;
        } else {
            while (($handlers = $this->handlers) === null) {
                $this->bake();
            }
            return $handlers;
        }
    }