Find the placename with the largest population and return its country.
        More population is a rough measure of importance.

        Paramaters
        ----------
        results: dict
            output of `query_geonames`

        Returns
        -------
        most_pop: str
            ISO code of country of place with largest population,
            or empty string if none

def _feature_most_population(self, results):
        """
        Find the placename with the largest population and return its country.
        More population is a rough measure of importance.

        Paramaters
        ----------
        results: dict
            output of `query_geonames`

        Returns
        -------
        most_pop: str
            ISO code of country of place with largest population,
            or empty string if none
        """

        try:
            populations = [i['population'] for i in results['hits']['hits']]
            most_pop = results['hits']['hits'][np.array(populations).astype("int").argmax()]
            return most_pop['country_code3']
        except Exception as e:
            return ""