code: def package_description(self):
          
          abstract = self.article.root.xpath('./front/article-meta/abstract')
          return serialize(abstract[0], strip=True) if abstract else None
docs: Given an Article class instance, this is responsible for returning an
          article description. For this method I have taken the approach of
          serializing the article's first abstract, if it has one. This results
          in 0 or 1 descriptions per article.