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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 is_unique(self):
 """True if no duplicate entries."""

        if self._is_unique is None:
            t = self.values[:-1] == self.values[1:]  # type: np.ndarray
            self._is_unique = ~np.any(t)
        return self._is_unique