code: public WRadioButton addRadioButton(final Object value) {
  		WRadioButton radioButton = new WRadioButton(this);
  		radioButton.setData(value);
  		return radioButton;
  	}
docs: This method will add a radio button to the group with the given value. The value must be unique for the group.
  <p>
  The radio button returned by this method must be added to the required location in the UI Component tree.
  </p>
  <p>
  The radio button group uses the {@link String} representation of the radio button's value to identify which
  button has been selected. As the string representation of the radio button's value is sent to the client, be
  mindful that it should not be too large.
  </p>
  
  @param value a unique value for the radio button.
  @return the radio button that was added to the group