+int btr_exec(struct btr_node *btrn, const char *command, char **value_result);
+int btr_exec_up(struct btr_node *btrn, const char *command, char **value_result);
+int btr_splice_out_node(struct btr_node *btrn);
+void btr_pushdown(struct btr_node *btrn);
+void *btr_context(struct btr_node *btrn);