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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 set_bounds(self, lb, ub):
 """ Change the lower and upper bounds of a variable. """

        if lb is not None and ub is not None and lb > ub:
            raise ValueError(
                "The provided lower bound {} is larger than the provided upper bound {}".format(lb, ub)
            )
        self._lb = lb
        self._ub = ub
        if self.problem is not None:
            self.problem._pending_modifications.var_lb.append((self, lb))
            self.problem._pending_modifications.var_ub.append((self, ub))