code: public List<String> getIndexNames() {
          List<String> indexNames = new ArrayList<String>(requests.size());
          for (IndexRequest request : requests) {
              if (request.getName() != null) {
                  indexNames.add(request.getName());
              } else {
                  indexNames.add(IndexHelper.generateIndexName(request.getKeys()));
              }
          }
          return indexNames;
      }
docs: Gets the index names.
  
  @return a list of index names