code: public List<IndexHolder> getUniqueIndexHolders() {
          List<IndexHolder> result = newArrayList();
  
          for (IndexHolder ih : indexHoldersByName.values()) {
              if (ih.isUnique()) {
                  result.add(ih);
              }
          }
  
          return result;
      }
docs: /*
  Returns the Index List that represent unique constraints.