code: public Collection<GlobalSecondaryIndex> globalSecondaryIndexes() {
          if (globalSecondaryIndexes.isEmpty()) {
              return null;
          }
          final Collection<GlobalSecondaryIndex> copies = new ArrayList<GlobalSecondaryIndex>(globalSecondaryIndexes.size());
          for (final String indexName : globalSecondaryIndexes.keySet()) {
              copies.add(globalSecondaryIndex(indexName));
          }
          return copies;
      }
docs: Gets the global secondary indexes for the given class.
  @return The map of index name to GlobalSecondaryIndexes.