title: how to combine two nodes into one group in Xpath?
body: <p>I have html like this:</p>
  
  <pre><code>&lt;div&gt;
      &lt;div class="a"&gt;10&lt;/div&gt;
      &lt;div class="b"&gt;11&lt;/div&gt;
      &lt;div class="a"&gt;20&lt;/div&gt;
      &lt;div class="b"&gt;21&lt;/div&gt;
  
  &lt;/div&gt;
  </code></pre>
  
  <p>Sometimes I use <code>//div[@class="a" or @class="b"]</code> to get four groups: <code>[10, 11, 20, 21]</code>.</p>
  
  <p>But this time I want to get something like this, two groups: <code>["10 11", "20 21"]</code>, could I?</p>
  
  <p>I mean that how to combine two nodes(class a, class b) into one group?</p>