code: def __fetch_data(self, url):
          
          url += '&api_key=' + self.api_key
          try:
              response = urlopen(url)
              root = ET.fromstring(response.read())
          except HTTPError as exc:
              root = ET.fromstring(exc.read())
              raise ValueError(root.get('message'))
          return root
docs: helper function for fetching data given a request URL