GeneratorManager not found

[SandStorm-dev]

2020-05-15 [07:51:25] [Server thread/CRITICAL]: Error: "Class 'pocketmine\world\generator\GeneratorManager' not found" (EXCEPTION) in "plugins/VanillaGenerator-master/src/muqsit/vanillagenerator/Loader" at line 15
2020-05-15 [07:51:25] [Server thread/DEBUG]: #0 src/pocketmine/plugin/PluginManager(180): muqsit\vanillagenerator\Loader->onLoad()
2020-05-15 [07:51:25] [Server thread/DEBUG]: #1 src/pocketmine/plugin/PluginManager(335): pocketmine\plugin\PluginManager->loadPlugin(string[45] /root/server/plugins/VanillaGenerator-master, array[1])
2020-05-15 [07:51:25] [Server thread/DEBUG]: #2 plugins/PocketMine-DevTools.phar/src/DevTools/DevTools(69): pocketmine\plugin\PluginManager->loadPlugins(string[22] /root/server/plugins/, array[1])
2020-05-15 [07:51:25] [Server thread/DEBUG]: #3 src/pocketmine/plugin/PluginBase(115): DevTools\DevTools->onEnable()
2020-05-15 [07:51:25] [Server thread/DEBUG]: #4 src/pocketmine/plugin/PluginManager(541): pocketmine\plugin\PluginBase->setEnabled(boolean 1)
2020-05-15 [07:51:25] [Server thread/DEBUG]: #5 src/pocketmine/Server(1783): pocketmine\plugin\PluginManager->enablePlugin(object DevTools\DevTools)
2020-05-15 [07:51:25] [Server thread/DEBUG]: #6 src/pocketmine/Server(1769): pocketmine\Server->enablePlugin(object DevTools\DevTools)
2020-05-15 [07:51:25] [Server thread/DEBUG]: #7 src/pocketmine/Server(1528): pocketmine\Server->enablePlugins(integer 0)
2020-05-15 [07:51:25] [Server thread/DEBUG]: #8 src/pocketmine/PocketMine(272): pocketmine\Server->__construct(object BaseClassLoader, object pocketmine\utils\MainLogger, string[14] /root/server/, string[22] /root/server/plugins/)
2020-05-15 [07:51:25] [Server thread/DEBUG]: #9 src/pocketmine/PocketMine(295): pocketmine\server()
2020-05-15 [07:51:25] [Server thread/DEBUG]: #10 (11): require(string[69] phar:///root/server/PocketMine-MP.phar/src/pocketmine/PocketMine.php)
2020-05-15 [07:51:25] [Server thread/CRITICAL]: Could not load plugin 'VanillaGenerator'

[Muqsit]

Simply, do not use it on API 3. Bumping API version isn't going to get you far, dude.