[Jupyter Notebook] Cannot load img with relative path
**Describe the bug**
I cannot load image with relative path in Jupyter Notebook.  
> pyxel.image(0).load(0, 0, "asset\cat_16x16.png")
>> FileNotFoundError: [Errno 2] No such file or directory: 'C:\\Users\\my_user_name\\Anaconda3\\envs\\pyxel\\lib\\asset\\cat_16x16.png'

when I use pwd,
> 'C:\\code\\..\\pyxel

Is it possible read img in current directory in Jupyter Notebook?

I can load image with absolute path, and example codes work successful.