将attr应用到第一级

<li class="page_item"><a href="/go.html?url=javascript:">A</a>
<ul class="children">
    <li class="page_item"><a href="/go.html?url=">1</a></li>
    <li class="page_item"><a href="/go.html?url=">2</a></li>
</ul>
</li>
<li class="page_item "><a href="/go.html?url=">B</a>
<ul class="children">
    <li class="page_item"><a href="/go.html?url=">1</a></li>
    <li class="page_item"><a href="/go.html?url=">2</a></li>
    <li class="page_item"><a href="/go.html?url=">3</a></li>
    <li class="page_item"><a href="/go.html?url=">4</a></li>
</ul>
</li>

<li class="page_item "><a href="/go.html?url=">C</a>
<ul class="children">
    <li class="page_item"><a href="/go.html?url=">1</a></li>
    <li class="page_item"><a href="/go.html?url=">2</a></li>
    <li class="page_item"><a href="/go.html?url=">3</a></li>
    <li class="page_item"><a href="/go.html?url=">4</a></li>
</ul>
<li class="page_item"><a href="/go.html?url=jav