code: def affiliation(self):
          
          out = []
          aff = namedtuple('Affiliation', 'id name city country')
          affs = listify(self._json.get('affiliation', []))
          for item in affs:
              new = aff(id=item.get('@id'), name=item.get('affilname'),
                        city=item.get('affiliation-city'),
                        country=item.get('affiliation-country'))
              out.append(new)
          return out or None
docs: A list of namedtuples representing listed affiliations in
          the form (id, name, city, country).
          Note: Might be empty.