'Fits an AFT model and returns parameters.
Parameters
None
Returns
Fitted params
Notes
To avoid dividing by zero, max(endog) is assumed to be uncensored.'

def params(self):

    self.model.modif_censors = np.copy(self.model.censors)
    self.model.modif_censors[(-1)] = 1
    wts = self.model._make_km(self.model.endog, self.model.modif_censors)
    res = WLS(self.model.endog, self.model.exog, wts).fit()
    params = res.params
    return params
