Just [tested this more](https://repl.it/languages/python3) and found out what the error was:

If you include the single quotes around the array, both statements return True

    stringList = '["list","of","strings"]'
    print("list" in stringList)
    True
    print ("li" in stringList)
    True

But if you remove the single quotes around the array, it functions as intended:

    stringList = ["list","of","strings"]
    print("list" in stringList)
    True
    print ("li" in stringList)
    False

Hope this helps!