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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 column_signs_(self):
 """ Return a numpy array with expected signs of features. Values are * +1 when all known terms which map to the column have positive sign; * -1 when all known terms which map to the column have negative sign; * ``nan`` when there are both positive and negative known terms for this column, or when there is no known term which maps to this column. """

        if self._always_positive():
            return np.ones(self.n_features)
        self.unhasher.recalculate_attributes()
        return self.unhasher.column_signs_