docs: def plot_sediment_rate(self, ax=None):
          """Plot sediment accumulation rate prior and posterior distributions"""
          if ax is None:
              ax = plt.gca()
  
          y_prior, x_prior = self.prior_sediment_rate()
          ax.plot(x_prior, y_prior, label='Prior')
  
          y_posterior = self.mcmcfit.sediment_rate
          density = scipy.stats.gaussian_kde(y_posterior.flat)
          density.covariance_factor = lambda: 0.25
          density._compute_covariance()
          ax.plot(x_prior, density(x_prior), label='Posterior')
  
          acc_shape = self.mcmcsetup.mcmc_kws['acc_shape']
          acc_mean = self.mcmcsetup.mcmc_kws['acc_mean']
          annotstr_template = 'acc_shape: {0}\nacc_mean: {1}'
          annotstr = annotstr_template.format(acc_shape, acc_mean)
          ax.annotate(annotstr, xy=(0.9, 0.9), xycoords='axes fraction',
                      horizontalalignment='right', verticalalignment='top')
  
          ax.set_ylabel('Density')
          ax.set_xlabel('Acc. rate (yr/cm)')
          ax.grid(True)
          return ax