Having trouble using playdate.menu.item

I'm trying to make a dynamic playdate menu by adding/deleting menu item when we join or exit the levels. Unfortunately I have trouble using the playdate.menu.item as I couldn't find any exemple in the Examples folder from the PlaydateSDK.

What is wrong with my code here ? :

local menu = playdate.getSystemMenu()

function ResetLevel()
    LoadLevel()
end
function ExitLevel()
	gameState = "inMenu"

    menu:removeMenuItem(menuItemReset)
    menu:removeMenuItem(menuItemExit)
end

menuItemReset = playdate.menu.item
menuItemReset:setCallback(ResetLevel)
menuItemReset:setTitle("Reset level")

menuItemExit = playdate.menu.item
menuItemExit:setCallback(ExitLevel)
menuItemExit:setTitle("Exit level")

function LoadLevel()
-- code happening

    if gameState == "inMenu" then
        menu:addMenuItem(menuItemReset)
        menu:addMenuItem(menuItemExit)
    end
    gameState = "inGame"
end

To create these menu items, you'll want to use playdate.menu:addMenuItem(title, callback), like so:

menuItemReset = menu:addMenuItem("Reset level", ResetLevel)

menuItemExit = menu:addMenuItem("Exit level", ExitLevel)