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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 group_by(self, *columns):
 """ Add a "group by" clause to the query :param columns: The columns to group by :type columns: tuple :return: The current QueryBuilder instance :rtype: QueryBuilder """

        for column in columns:
            self.groups.append(column)

        return self