code: def set_computable_distance(self, value):
          ''' setter '''
          if isinstance(value, ComputableDistance) is False:
              raise TypeError()
          self.__computable_distance = valuf set_computable_distance(self, value):
          ''' setter '''
          if isinstance(value, ComputableDistance) is False:
              raise TypeError()
          self.__computable_distance = value
docs: setter