code: public Iterable<String> get(String index, Iterable<String> keys) {
          Multimap<String, String> mmap = get(index);
          IterableChain<String> result = new IterableChain<String>();
          for (String key : keys) {
              result.addAll(mmap.get(key));
          }
          return result;
      }
docs: get the values stored for the given {@code index} and {@code keys}