int def_foreach (graph_def_t *def, def_callback_t callback, void *user_data);
int def_get_rrdargs (graph_def_t *def, graph_ident_t *ident,
int def_foreach (graph_def_t *def, def_callback_t callback, void *user_data);
int def_get_rrdargs (graph_def_t *def, graph_ident_t *ident,