code: def get_computed_cost_arr(self):
          ''' getter '''
          if isinstance(self.__computed_cost_arr, np.ndarray):
              return self.__computed_cost_arr
          else:
              raise TypeError(f get_computed_cost_arr(self):
          ''' getter '''
          if isinstance(self.__computed_cost_arr, np.ndarray):
              return self.__computed_cost_arr
          else:
              raise TypeError()
docs: getter