code: def score_(self):
          
          # pylint: disable=access-member-before-definition
          if hasattr(self, "_predicted_median"):
              self._concordance_score_ = concordance_index(self.durations, self._predicted_median, self.event_observed)
              del self._predicted_median
              return self._concordance_score_
          return self._concordance_score_
docs: The concordance score (also known as the c-index) of the fit.  The c-index is a generalization of the ROC AUC
          to survival data, including censorships.
  
          For this purpose, the ``score_`` is a measure of the predictive accuracy of the fitted model
          onto the training dataset.