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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 up(self) -> "InstanceNode": """Return an instance node corresponding to the receiver's parent. Raises: NonexistentInstance: If there is no parent. """

        ts = max(self.timestamp, self.parinst.timestamp)
        return self.parinst._copy(self._zip(), ts)