code: def variance(self):
          '''
          Compute variance.
  
          Returns:
              variance.
          '''
          alpha = self.__success + self.__default_alpha
          beta = self.__failure + self.__default_beta
  
          try:
              variance = alpha * beta / ((alpha + beta) ** 2) * (alpha + beta + 1)
          except ZeroDivisionError:
              variance = 0.0
          return variancf variance(self):
          '''
          Compute variance.
  
          Returns:
              variance.
          '''
          alpha = self.__success + self.__default_alpha
          beta = self.__failure + self.__default_beta
  
          try:
              variance = alpha * beta / ((alpha + beta) ** 2) * (alpha + beta + 1)
          except ZeroDivisionError:
              variance = 0.0
          return variance
docs: Compute variance.
  
          Returns:
              variance.