def EU27as(self, to='name_short'):
        """
        Return EU27 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

        """
        if isinstance(to, str):
            to = [to]
        return self.data[self.data.EU < 2013][to]
Return EU27 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