code: @SuppressWarnings("unchecked")
    protected <T> T get(DBIDRef id, int index) {
      Object[] d = data.get(DBIDUtil.deref(id));
      if(d == null) {
        return null;
      }
      return (T) d[index];
    }
docs: Actual getter.
  
  @param id Database ID
  @param index column index
  @param <T> type
  @return current value