How to raise own error when one positional argument is missing?I have this function that inserts a line at a given index called num.python will raise an error if no num is given but I want to raise my own error.How do I do that?This is what I tried.

def insertNum(self, num, line): if num== None: raise Exception("Num not specified.") else: self.list.insert(num, line) return self.list

But it doesn't work pleaseee helpp