code: int[] getKeys()
      {
          Set<Integer> keySet = map.keySet();
          int keys[] = new int[keySet.size()];
          int index = 0;
          for (Integer key : keySet)
          {
              keys[index] = key;
              index++;
          }
          return keys;
      }
docs: Package private method to obtain the keys stored in these
  options. Also used on native side.
  
  @return The keys of these options