fun setGroup(playername: String, groupName: String){
    //Check if player exist
    var offlinePlayer = BandiCore.instance!!.server.getOfflinePlayer(playername)
    if(offlinePlayer == null){
        throw PlayerNotFoundException()
    }
    //Check if group exist
    var group = BandiCore.luckpermsAPI!!.groupManager.getGroup(groupName)
    if(group == null){
        throw GroupNotFoundException()
    }
    BandiCore.luckpermsAPI!!.getUserManager().modifyUser(offlinePlayer.getUniqueId()) { user: User ->
        // Remove all other inherited groups the user had before.
        user.data().clear(NodeType.INHERITANCE::matches)
        // Create a node to add to the player.
        val node: Node = InheritanceNode.builder(group).build()
        // Add the node to the user.
        user.data().add(node)
        // Tell the sender.
        throw GroupChangedException()
    }
}