private short getVersionComparisonGroup() {
    switch (version) {
      case BLOB_ID_V1:
        return 1;
      case BLOB_ID_V2:
        return 2;
      case BLOB_ID_V3:
      case BLOB_ID_V4:
      case BLOB_ID_V5:
        return 3;
      case BLOB_ID_V6:
        return 4;
      default:
        throw new IllegalArgumentException("Unrecognized blobId version " + version);
    }
  }
This gets a "version comparison group" to be used in the {@link #compareTo} method. If two blob IDs are in
different groups, they cannot be deemed equal to each other. This allows for comparison strategies that rely
on version-specific features or fields.
@return the "version comparison group" number.
ambry-commons/src/main/java/com/github/ambry/commons/BlobId.java