code: public static List<String> getCallSetsNames(String variantSetId, OfflineAuth auth)
        throws IOException {
      List<String> output = Lists.newArrayList();
      Genomics genomics = GenomicsFactory.builder().build().fromOfflineAuth(auth);
      Iterable<CallSet> cs = Paginator.Callsets.create(genomics)
          .search(new SearchCallSetsRequest().setVariantSetIds(Lists.newArrayList(variantSetId)),
              "callSets(name),nextPageToken");
      for (CallSet c : cs) {
        output.add(c.getName());
      }
      if (output.isEmpty()) {
        throw new IOException("VariantSet " + variantSetId + " does not contain any CallSets");
      }
      return output;
    }
docs: Gets CallSets Names for a given variantSetId using the Genomics API.
  
  @param variantSetId The id of the variantSet to query.
  @param auth The OfflineAuth for the API request.
  @return The list of callSet names in the variantSet.
  @throws IOException If variantSet does not contain any CallSets.