code: def extended(self) -> ListP:
          
          parts = [part.extended for part in self.parts]
          return ListP([_Concatenated(parts), String.build(self.subtype),
                        _ParamsList(self.content_type_params),
                        String.build(self.content_disposition),
                        String.build(self.content_language),
                        String.build(self.content_location)])
docs: The body structure attributes with extension data.