code: def get_target_n(self):
          ''' getter '''
          if isinstance(self.__target_n, int) is False:
              raise TypeError("The type of __target_n must be int.")
          return self.__target_f get_target_n(self):
          ''' getter '''
          if isinstance(self.__target_n, int) is False:
              raise TypeError("The type of __target_n must be int.")
          return self.__target_n
docs: getter