docs: def update(self, ell, k):
          """Update the posterior and estimates after a label is sampled
  
          Parameters
          ----------
          ell : int
              sampled label: 0 or 1
  
          k : int
              index of stratum where label was sampled
          """
          self.alpha_[k] += ell
          self.beta_[k] += 1 - ell
  
          self._calc_theta()
          if self.store_variance:
              self._calc_var_theta()