code: private boolean updateExistingObject(DBObject dbObj, Map<String, String> currScalarMap) {
          if (objectIsChangingShards(dbObj, currScalarMap)) {
              return updateShardedObjectMove(dbObj);
          } else {
              return updateObjectSameShard(dbObj, currScalarMap);
          }
      }
docs: Update the given object using the appropriate strategy.