Fit MCMC AgeDepthModel

def fit(self):
        """Fit MCMC AgeDepthModel"""
        self._mcmcfit = self.mcmcsetup.run()
        self._mcmcfit.burnin(self.burnin)
        dmin = min(self._mcmcfit.depth_segments)
        dmax = max(self._mcmcfit.depth_segments)
        self._thick = (dmax - dmin) / len(self.mcmcfit.depth_segments)
        self._depth = np.arange(dmin, dmax + 0.001)
        self._age_ensemble = np.array([self.agedepth(d=dx) for dx in self.depth])