code: def articles(self):
          
          if self._articles is None:
              self._articles = []
              for doc in self.docs:
                  # ensure all fields in the "fl" are in the doc to address
                  # issue #38
                  for k in set(self.fl).difference(doc.keys()):
                      doc[k] = None
                  self._articles.append(Article(**doc))
          return self._articles
docs: articles getter