code: def extended(self) -> ListP:
          
          return ListP([String.build(self.maintype), String.build(self.subtype),
                        _ParamsList(self.content_type_params),
                        String.build(self.content_id),
                        String.build(self.content_description),
                        String.build(self.content_transfer_encoding,
                                     fallback=b'7BIT'),
                        Number(self.size),
                        String.build(self.body_md5),
                        String.build(self.content_disposition),
                        String.build(self.content_language),
                        String.build(self.content_location)])
docs: The body structure attributes with extension data.