docs: public void addFamilyWithUnionRule() {
      System.out.printf("%nCreating column family %s with union GC rule%n", COLUMN_FAMILY_3);
      // [START bigtable_create_family_gc_union]
      // Creates a column family with GC policy to drop data that matches at least one condition.
  
      // Defines a list of GC rules to drop cells older than 5 days OR not the most recent
      // version.
      UnionRule unionRule =
          GCRULES.union().rule(GCRULES.maxAge(5, TimeUnit.DAYS)).rule(GCRULES.maxVersions(1));
  
      // Creates column family with given GC rule.
      try {
        // ModifyColumnFamiliesRequest can be used both for adding and modifying families, here it is
        // being used to add a family
        ModifyColumnFamiliesRequest columnFamiliesRequest =
            ModifyColumnFamiliesRequest.of(tableId).addFamily(COLUMN_FAMILY_3, unionRule);
        adminClient.modifyFamilies(columnFamiliesRequest);
        System.out.println("Created column family: " + COLUMN_FAMILY_3);
      } catch (AlreadyExistsException e) {
        System.err.println(
            "Failed to create column family with rule, already exists: " + e.getMessage());
      }
      // [END bigtable_create_family_gc_union]
    }