code: def hidden(self):
          
          members = [self.member_info(item["_id"]) for item in self.members()]
          result = []
          for member in members:
              if member['rsInfo'].get('hidden'):
                  server_id = member['server_id']
                  result.append({
                      '_id': member['_id'],
                      'host': self._servers.hostname(server_id),
                      'server_id': server_id})
          return result
docs: return list of hidden members