code: def add_weight(self, weight):
          
          if weight is None:
              raise NullArgument('weight cannot be None')
          if not self.my_osid_object_form._is_valid_decimal(
                  weight, self.get_weight_metadata()):
              raise InvalidArgument('weight')
          self.my_osid_object_form._my_map['weight'] = weight
docs: stub