How to check if argument is in config

config:

PHP:

kits:
   starter:
       items: 276:0:1
   star:
       items: 299:0:1

how do i check if args[0](lets say 'starter') is under kits?

 

If $getConfig() == $args[0]?

 

PHP:

[Server thread/CRITICAL]: Unhandled exception executing command 'warp ccc' in warp: Cannot use object of type pocketmine\utils\Config as array
[18:04:45] [Server thread/CRITICAL]: Error: "Cannot use object of type pocketmine\utils\Config as array" (EXCEPTION) in "test/src/gay/command/warp/Command" at line 36

PHP:

if(isset($this->core->config["Warps"][$args[0]])){
                    $sender->sendMessage("in config");
                }else{
                    $sender->sendMessage("not in config");
                }