code: def label_for_value(self, value, key=None):
          
          if not key:
              key = self.rel.get_related_field().name
  
          if value is not None:
              try:
                  obj = self.model._default_manager.using(self.db).get(**{key: value})
                  return force_unicode(obj)
              except (ValueError, self.model.DoesNotExist):
                  return ''
          return ''
docs: Looks up the current value of the field and returns
          a unicode representation. Default implementation does a lookup
          on the target model and if a match is found calls force_unicode
          on that object. Otherwise a blank string is returned.