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_append_ap(sd_bus_message *m, const char *types, va_list ap);
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int bus_message_parse_fields(sd_bus_message *m);
struct bus_body_part *message_append_part(sd_bus_message *m);