Bootstrap multiselect下拉菜单从optgroup中取消选择相同的值选项

<select id="mySelect" multiple>
  <optgroup label="Group 1">
    <option value="1">Option 1</option>
    <option value="2">Option 2</option>
    <option value="3">Option 3</option>
  </optgroup>
  <optgroup label="Group 2">
    <option value="4">Option 4</option>
    <option value="5">Option 5</option>
    <option value="6">Option 6</option>
  </optgroup>
</select>

$(document).ready(function() {
  $('#mySelect').multiselect({
    nonSelectedText: 'Select an option',
    enableFiltering: true,
    enableCaseInsensitiveFiltering: true,
    buttonWidth: '200px'
  });
});

$('#mySelect').on('change', function() {
  var selectedValues = $(this).val();
  var uniqueValues = Array.from(new Set(selectedValues)); // 去除重复值
  $(this).multiselect('deselect', selectedValues); // 取消选择所有选项
  $(this).multiselect('select', uniqueValues); // 重新选择去重后的选项
});