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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def insert(self, var, value, index=None):
 """Insert at the index. If the index is not provided appends to the end of the list. """

        current = self.__get(var)
        if not isinstance(current, list):
            raise KeyError("%s: is not a list" % var)
        if index is None:
            current.append(value)
        else:
            current.insert(index, value)
        if self.auto_save:
            self.save()