+void xbt_set_remove (xbt_set_t set, xbt_set_elm_t elm);
+void xbt_set_remove_by_name (xbt_set_t set, const char *key);
+void xbt_set_remove_by_name_ext (xbt_set_t set, const char *key, int key_len);
+void xbt_set_remove_by_id (xbt_set_t set, int id);