Concordance index when using interval censoring

[wftfwtf]

Hi,

I have a quick quesiton (it may be a stupid question). When I used WeibullAFTFitter with interval censored data, the model did not return concordance index. Would you anyone please tell me the reason?

In the error message, WeibullAFTFitter does NOT have "durations" when I used interval censoring, but DOES have "durations" when I used right censoring.

wftL.concordance_index_
Traceback (most recent call last):

wftL =WeibullAFTFitter(penalizer=0.01)
#wftL =WeibullAFTFitter()

wftL.fit_interval_censoring(df2, lower_bound_col=var[0],upper_bound_col=var[1])

wftL.concordance_index_

Cell In[53], line 1
wftL.concordance_index_

File C:\ProgramData\Anaconda3\envs\lifelines\Lib\site-packages\lifelines\fitters_init_.py:2691 in concordance_index_
self.concordance_index = utils.concordance_index(self.durations, self._predicted_median, self.event_observed)

AttributeError: 'WeibullAFTFitter' object has no attribute 'durations'