code: public Map<String, Object> sub(Map<String, Object> data, String prefix) {
      return sub(data, prefix, null, true);
    }
docs: <p>
  sub.
  </p>
  
  @param data a {@link java.util.Map} object.
  @param prefix a {@link java.lang.String} object.
  @return a {@link java.util.Map} object.