jQuery Select2 -如何隐藏Select2 Optgroup

<select id="mySelect">
  <optgroup label="Group 1">
    <option value="1">Option 1</option>
    <option value="2">Option 2</option>
  </optgroup>
  <optgroup label="Group 2">
    <option value="3">Option 3</option>
    <option value="4">Option 4</option>
  </optgroup>
</select>

$(document).ready(function() {
  $('#mySelect').select2({
    templateSelection: function(data, container) {
      if (data.element && data.element.parentElement.tagName === 'OPTGROUP') {
        $(container).addClass('hidden');
      }
      return data.text;
    }
  });
});

.hidden {
  display: none;
}