code: def predict_median(self, X, ancillary_X=None):
          
          return self.predict_percentile(X, p=0.5, ancillary_X=ancillary_X)
docs: Predict the median lifetimes for the individuals. If the survival curve of an
          individual does not cross 0.5, then the result is infinity.
  
          Parameters
          ----------
          X: numpy array or DataFrame
              a (n,d) covariate numpy array or DataFrame. If a DataFrame, columns
              can be in any order. If a numpy array, columns must be in the
              same order as the training data.
          ancillary_X: numpy array or DataFrame, optional
              a (n,d) covariate numpy array or DataFrame. If a DataFrame, columns
              can be in any order. If a numpy array, columns must be in the
              same order as the training data.
  
          Returns
          -------
          percentiles: DataFrame
              the median lifetimes for the individuals. If the survival curve of an
              individual does not cross 0.5, then the result is infinity.
  
  
          See Also
          --------
          predict_percentile, predict_expectation