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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 add(self, variable, range_):
 """ Add a new low and high bound for a variable. As it is flow insensitive, it compares it with old values and update it if needed. """

        if variable not in self.result:
            self.result[variable] = range_
        else:
            self.result[variable] = self.result[variable].union(range_)
        return self.result[variable]