Yen3

Thanks for @qrux0 and @amgoyal's comment. They give me the idea. Maybe we don't have to rewrite `` and ``. We can add two function to push/pop the trace stack....

The [jedi-vim](https://github.com/davidhalter/jedi-vim/blob/master/pythonx/jedi_vim.py#L329-L345) uses a trick to insert tags into vim's original stack. The benefit of the method is that the implementation does not need to manipulate a stack to memory...

I meet one problem. When I try to call `tornado.process.Subprocess.wait_for_exit()` function, the pytest-tornado will hang. I don't the problem is like what @wouterdb mentioned or not. The test code is...