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.

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_