code: def to_protobuf(self) -> SaveStateProto:
          
          result = SaveStateProto()
          result.version = str(self.version)
          result.last_update.CopyFrom(datetime_to_timestamp(self.last_update))
          result.plugin_info.CopyFrom(self.plugin_info.to_protobuf())
          for key, link_item in self.link_item_dict.items():
              result.data[key].CopyFrom(link_item.to_protobuf())
          return result
docs: Create protobuf item.
  
          :return: protobuf structure
          :rtype: ~unidown.plugin.protobuf.save_state_pb2.SaveStateProto