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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 diff(self, diff):
 """ Serialize to a dictionary. """

        if diff is None:
            return None
        return dict(
            toVol=diff.toUUID,
            fromVol=diff.fromUUID,
            size=diff.size,
            sizeIsEstimated=diff.sizeIsEstimated,
        )