code: def get_alpha_value(self):
          '''
          getter
          Learning rate.
          '''
          if isinstance(self.__alpha_value, float) is False:
              raise TypeError("The type of __alpha_value must be float.")
          return self.__alpha_valuf get_alpha_value(self):
          '''
          getter
          Learning rate.
          '''
          if isinstance(self.__alpha_value, float) is False:
              raise TypeError("The type of __alpha_value must be float.")
          return self.__alpha_value
docs: getter
          Learning rate.