code: public boolean isBaseLevelForKey(Slice userKey)
      {
          // Maybe use binary search to find right entry instead of linear search?
          UserComparator userComparator = inputVersion.getInternalKeyComparator().getUserComparator();
          for (int level = this.level + 2; level < NUM_LEVELS; level++) {
              List<FileMetaData> files = inputVersion.getFiles(level);
              while (levelPointers[level] < files.size()) {
                  FileMetaData f = files.get(levelPointers[level]);
                  if (userComparator.compare(userKey, f.getLargest().getUserKey()) <= 0) {
                      // We've advanced far enough
                      if (userComparator.compare(userKey, f.getSmallest().getUserKey()) >= 0) {
                          // Key falls in this file's range, so definitely not base level
                          return false;
                      }
                      break;
                  }
                  levelPointers[level]++;
              }
          }
          return true;
      }
docs: in levels greater than "level+1".