int gl_graph_instance_get_all (graph_config_t *cfg, graph_inst_callback_t callback,
void *user_data);
int gl_instance_get_all (graph_inst_callback_t callback, void *user_data);
int gl_graph_instance_get_all (graph_config_t *cfg, graph_inst_callback_t callback,
void *user_data);
int gl_instance_get_all (graph_inst_callback_t callback, void *user_data);