'customPopupHtml' how to set css style?

[qiushi0908]

I get popupView background is black; It is not my mind; And i how to setup style with pupupView?
Is lick this?

  customPopupHtml = task => {
    return `
    <style type="text/css">
    .details-container {
       width: 160px;
       background: #fff;
    }
    </style>
    <div class="details-container">
          <h5>${task.name}</h5>
          <p>Expected to finish by ${task._end}</p>
          <p>${task.progress}% completed!</p>
    </div>
    `;
  };

But the pupUpView bottom and top margin is still black!