int bus_message_get_arg(sd_bus_message *m, unsigned i, const char **str);
int bus_message_get_arg_strv(sd_bus_message *m, unsigned i, char ***strv);
int bus_message_get_arg(sd_bus_message *m, unsigned i, const char **str);
int bus_message_get_arg_strv(sd_bus_message *m, unsigned i, char ***strv);