def fit(self, durations, event_observed=None, timeline=None, entry=None,
            label='BFH_estimate', alpha=None, ci_labels=None):
        self._label = label
        alpha = alpha if alpha is not None else self.alpha

        naf = NelsonAalenFitter(alpha)
        naf.fit(durations, event_observed=event_observed, timeline=timeline, label=label, entry=entry, ci_labels=ci_labels)
        self.durations, self.event_observed, self.timeline, self.entry, self.event_table = \
            naf.durations, naf.event_observed, naf.timeline, naf.entry, naf.event_table

        # estimation
        self.survival_function_ = np.exp(-naf.cumulative_hazard_)
        self.confidence_interval_ = np.exp(-naf.confidence_interval_)
        self.median_ = median_survival_times(self.survival_function_)

        # estimation methods
        self.predict = self._predict("survival_function_", label)
        self.subtract = self._subtract("survival_function_")
        self.divide = self._divide("survival_function_")

        # plotting functions
        self.plot = self._plot_estimate("survival_function_")
        self.plot_survival_function = self.plot
        return self
Instantiating L{ssl.DefaultOpenSSLContextFactory} with a certificate
dataset/ETHPy150Open CamDavidsonPilon/lifelines/lifelines/fitters/breslow_fleming_harrington_fitter.py/BreslowFlemingHarringtonFitter.fit--crossover with--dataset/ETHPy150Open twisted/twisted/twisted/test/test_ssl.py/DefaultOpenSSLContextFactoryTests.test_missingCertificateFile