title: how to parse nested html tag using xpath
body: <p>This is my sample html code.</p>
  
  <p>using HtmlXpathSelector i need to parse the html file.</p>
  
  <p>def parse(self, response):
      edxData = HtmlXpathSelector(response)</p>
  
  <ol>
  <li>first i need to get all the tag which contain 
  edxData.xpath('//h2[@class = "title course-title"]')</li>
  <li>inside of that tag i need to check a tag value.</li>
  <li>then need to parse the div tag with class name subtitle course-subtitle copy-detail.
  how can i parse this value kindly give some suggestion</li>
  </ol>
  
  <p>sample html response data:</p>
  
  <pre><code> &lt;html&gt;
   &lt;body&gt;
   &lt;h2 class="title course-title"&gt;
   &lt;a href="https://www.edx.org/course/mitx/mitx-14-73x-challenges-global-poverty-1350"&gt;The Challenges of Global Poverty
   &lt;/a&gt;
   &lt;/h2&gt; 
   &lt;div class="subtitle course-subtitle copy-detail"&gt;A course for those who are interested in the challenge posed by massive and persistent world poverty.
   &lt;/div&gt;
   &lt;/body&gt;
   &lt;/html&gt;  
  </code></pre>