Yii2 checkbox group with bootstrap 3

How to create checkbox group in yii2?

That's what we need

<div class="btn-group" data-toggle="buttons">
  <label class="btn btn-primary active">
    <input type="checkbox" autocomplete="off" checked> Checkbox 1 (pre-checked)
  </label>
  <label class="btn btn-primary">
    <input type="checkbox" autocomplete="off"> Checkbox 2
  </label>
  <label class="btn btn-primary">
    <input type="checkbox" autocomplete="off"> Checkbox 3
  </label>
</div>

That's what I have

<?
    $options = ['uncheck'=>0];

    echo ButtonGroup::widget([
        'options' => [
            'data-toggle' => 'buttons'
        ],
        'buttons' => [
            $form->field($model, 'field1')->checkbox($options),
            $form->field($model, 'field2')->checkbox($options),
            $form->field($model, 'field3')->checkbox($options),
        ],
    ]);
?>

What I need to add in my code, to generate that markdown?