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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 fold(self, node):
 """Do constant folding."""

        node = self.generic_visit(node)
        try:
            return nodes.Const.from_untrusted(node.as_const(),
                                              lineno=node.lineno,
                                              environment=self.environment)
        except nodes.Impossible:
            return node