code: def UNas(self, to='name_short'):
          
          if isinstance(to, str):
              to = [to]
          return self.data[self.data.UNmember > 0][to]
docs: Return UN member states in the specified classification
  
          Parameters
          ----------
          to : str, optional
              Output classification (valid str for an index of
              country_data file), default: name_short
  
          Returns
          -------
          Pandas DataFrame