code: def EU28as(self, to='name_short'):
          
          if type(to) is str:
              to = [to]
          return self.data[self.data.EU < 2015][to]
docs: Return EU28 countries 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