docs: def assignees(self):
          """List of assignees to the activity."""
          if 'assignees' in self._json_data and self._json_data.get('assignees_ids') == list():
              return []
          elif 'assignees' in self._json_data and self._json_data.get('assignees_ids'):
              assignees_ids_str = ','.join([str(id) for id in self._json_data.get('assignees_ids')])
              return self._client.users(id__in=assignees_ids_str, is_hidden=False)
          return None