+function add_filter_hook(callback)
+ t_insert(new_filter_hooks, callback);
+end
+
+function remove_filter_hook(callback)
+ for i=1,#new_filter_hooks do
+ if new_filter_hooks[i] == callback then
+ t_remove(new_filter_hooks, i);
+ end
+ end
+end
+
+return _M;