@Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append(name).append("={");
    sb.append(StringUtils.join(tables, ','));
    sb.append("}");
    return sb.toString();
  }
Backup set is a named group of HBase tables, which are managed together by Backup/Restore
framework. Instead of using list of tables in backup or restore operation, one can use set's name
instead.
hbase-backup/src/main/java/org/apache/hadoop/hbase/backup/util/BackupSet.java