code: def _conditional_time_to_event_(self):
          
          age = self.survival_function_.index.values[:, None]
          columns = ["%s - Conditional time remaining to event" % self._label]
          return (
              pd.DataFrame(
                  qth_survival_times(self.survival_function_[self._label] * 0.5, self.survival_function_)
                  .sort_index(ascending=False)
                  .values,
                  index=self.survival_function_.index,
                  columns=columns,
              )
              - age
          )
docs: Return a DataFrame, with index equal to survival_function_, that estimates the median
          duration remaining until the death event, given survival up until time t. For example, if an
          individual exists until age 1, their expected life remaining *given they lived to time 1*
          might be 9 years.
  
          Returns
          -------
          conditional_time_to_: DataFrame
              with index equal to survival_function_