code: def affiliation_history(self):
          
          aff_ids = [e.attrib.get('affiliation-id') for e in
                     self.xml.findall('author-profile/affiliation-history/affiliation')
                     if e is not None and len(list(e.find("ip-doc").iter())) > 1]
          return [ScopusAffiliation(aff_id) for aff_id in aff_ids]
docs: List of ScopusAffiliation objects representing former
          affiliations of the author.  Only affiliations with more than one
          publication are considered.