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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_bug(self, bug_number):
 """ Set the bug number of this Classified Failure If an existing ClassifiedFailure exists with the same bug number replace this instance with the existing one. """

        if bug_number == self.bug_number:
            return self

        other = ClassifiedFailure.objects.filter(bug_number=bug_number).first()
        if not other:
            self.bug_number = bug_number
            self.save(update_fields=['bug_number'])
            return self

        self.replace_with(other)

        return other