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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 _values_for_argsort(self) -> np.ndarray: """Return values for sorting. Returns ------- ndarray The transformed values should maintain the ordering between values within the array. See Also -------- ExtensionArray.argsort """

        data = self._data.copy()
        data[self._mask] = data.min() - 1
        return data