def METHOD_NAME(self):
    self.zone_parser_functions: List[ZoneParserFunction] = []
    for model_map in [CONFIG_MODEL.exchanges, CONFIG_MODEL.zones]:
        for zone in model_map.keys():
            model = model_map[zone]
            if not model.parsers:
                continue
            for mode, function_name in model.parsers:
                if function_name is not None:
                    # load all functions
                    function = model.parsers.get_function(mode)
                    self.assertTrue(callable(function))
                    assert function
                    self.zone_parser_functions.append(
                        ZoneParserFunction(
                            zone=zone,
                            mode=mode,
                            function_name=function_name,
                            function=function,
                        )
                    )