code: public PdfFormField getRadioGroup(boolean noToggleToOff, boolean radiosInUnison) {
          PdfFormField field = PdfFormField.createRadioButton(writer, noToggleToOff);
          if (radiosInUnison)
              field.setFieldFlags(PdfFormField.FF_RADIOSINUNISON);
          field.setFieldName(fieldName);
          if ((options & READ_ONLY) != 0)
              field.setFieldFlags(PdfFormField.FF_READ_ONLY);
          if ((options & REQUIRED) != 0)
              field.setFieldFlags(PdfFormField.FF_REQUIRED);
          field.setValueAsName(checked ? onValue : "Off");
          return field;
      }
docs: Gets a radio group. It's composed of the field specific keys, without the widget
  ones. This field is to be used as a field aggregator with {@link PdfFormField#addKid(PdfFormField) addKid()}.
  @param noToggleToOff if <CODE>true</CODE>, exactly one radio button must be selected at all
  times; clicking the currently selected button has no effect.
  If <CODE>false</CODE>, clicking
  the selected button deselects it, leaving no button selected.
  @param radiosInUnison if <CODE>true</CODE>, a group of radio buttons within a radio button field that
  use the same value for the on state will turn on and off in unison; that is if
  one is checked, they are all checked. If <CODE>false</CODE>, the buttons are mutually exclusive
  (the same behavior as HTML radio buttons)
  @return the radio group