Hi @vsvvssrao! Unfortunately, we cannot help you if you do not give us any context. For instance, what version of tutor are your running? what is the full stacktrace? what global variable did you define?
In general, when asking for help, you should not expect other people to put in more effort in answering your question that you invested yourself in asking the question. Thus, if all you do is paste some traceback, then you should not expect anything better than a boilerplate answer (like this one).