html运行实例（bs_collapsible

代码示例：（标识：bs_collapsible_in）
<!DOCTYPE html>
<html lang="en">
<head>
  <title>Bootstrap 实例</title>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/css/bootstrap.min.css" rel="stylesheet">
  <script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/js/bootstrap.bundle.js"></script>
</head>
<body>

<div class="p-4">
  <h2>默认显示折叠的内容</h2>
  <p>在 collapse 类旁边添加 show 类，可默认显示内容。</p>
  <p>单击按钮可在显示和隐藏内容之间切换。</p>
  <button type="button" class="btn btn-primary" data-bs-toggle="collapse" data-bs-target="#demo">春日</button>
  <div id="demo" class="collapse show">
    <p>胜日寻芳泗水滨，无边光景一时新。</p>
    <p>等闲识得东风面，万紫千红总是春。</p>
  </div>
</div>

</body>
</html>