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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 _get_unknown_value(self):
 """ Finds the smallest integer value >=0 that is not in `labels` :return: Value that is not in the labels :rtype: int """

        label_set = set(self.labels)
        value = 0
        while value in label_set:
            value += 1
        return value