Comment utiliser la zone de sélection multiple déroulante de bootstrap

<!-- Latest compiled and minified CSS -->
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.10.0/css/bootstrap-select. 
min.css">
<!-- Latest compiled and minified JavaScript -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.10.0/js/bootstrap-select.min.js"></script>
<!-- (Optional) Latest compiled and minified JavaScript translation files -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.10.0/js/i18n/defaults-zh_CN.min.js"></script>

<select class="selectpicker" title="请选择">
    <option value="1">广东省</option>
    <option value="2">广西省</option>
    <option value="3">福建省</option>
    <option value="4">湖南省</option>
    <option value="5">山东省</option>   
</select>

<select class="form-control selectpicker" data-live-search="true" multiple>
        <optgroup label="广东省">
                <option value="1">广州市</option>
                <option value="2">深圳市</option>
                <option value="3">珠海市</option>
         </optgroup>   
          <optgroup label="广西">
                  <option value="1">南宁市</option>
                  <option value="2">柳州</option>
                  <option value="3">桂林市</option>
           </optgroup>  
           <optgroup label="山东">
                   <option value="1">烟台</option>
                   <option value="2">青岛</option>
                   <option value="3">济南</option>
             </optgroup>                          
</select>

<select class="selectpicker" data-style="btn-primary">
  ...
</select>
<select class="selectpicker" data-style="btn-info">
  ...
</select>
<select class="selectpicker" data-style="btn-success">
  ...
</select>
<select class="selectpicker" data-style="btn-warning">
  ...
</select>
<select class="selectpicker" data-style="btn-danger">
  ...
</select>

<select class="selectpicker" data-live-search="true">....</select>

<select class="selectpicker form-control" multiple data-max-options="2">...</select>

<select class="selectpicker" multiple data-live-search="true" data-live-search-placeholder="搜索" 
data-actions-box="true">
　　<optgroup label="filter1">
　　　　<option>option1</option>
　　　　<option selected>option2</option>
　　　　<option>option3</option>
　　　　<option>option4</option>
　　</optgroup>
　　<optgroup label="filter2">
　　　　<option>option1</option>
　　　　<option>option2</option>
　　　　<option>option3</option>
　　　　<option>option4</option>
　　</optgroup>
　　<optgroup label="filter3">
　　　　<option>option1</option>
　　　　<option>option2</option>
　　　　<option>option3</option>
　　　　<option>option4</option>
　　</optgroup>
</select>

$('.selectpicker').selectpicker('val','mustard');
$('.selectpicker').selectpicker('val',['mustard','relish']);

$('.selectpicker').selectpicker('refresh');

$('.selectpicker').on('changed.bs.select',function(e){
});