Returns: generator over all units of this group

def units(self) -> typing.Iterator['BaseUnit']:
        """
        Returns: generator over all units of this group
        """
        for unit_index in self._section_group['units']:
            if unit_index not in self.__units.keys():
                _category = self.units_class_enum[self.group_category]  # type: ignore
                self.__units[unit_index] = _category(self.d, self.l10n, self.coa_color,
                                                     self.country_index,
                                                     self.group_category,
                                                     self.group_index, unit_index)
            yield self.__units[unit_index]