code: def score_(self):
          
          # pylint: disable=access-member-before-definition
          if hasattr(self, "_predicted_hazards_"):
              self._concordance_score_ = concordance_index(self.durations, -self._predicted_hazards_, self.event_observed)
              del self._predicted_hazards_
              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. It's analogous to the R^2 in linear models.