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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 unmasked(self, depth=0.01):
 """Return the unmasked overfitting metric for a given transit depth."""

        return 1 - (np.hstack(self._O2) +
                    np.hstack(self._O3) / depth) / np.hstack(self._O1)