Returns: generator over all countries in this coalition

def countries(self) -> typing.Iterator['Country']:
        """
        Returns: generator over all countries in this coalition
        """
        for k in self._section_country:
            if k not in self._countries.keys():
                country = Country(self.d, self.l10n, self.coa_color, k)
                self._countries[k] = country
                self._countries_by_id[country.country_id] = country
                self._countries_by_name[country.country_name] = country
            yield self._countries[k]