Drop and Drag callback system

Hi everyone, I had been learning about python drag and drop system in TouchDesigner, so I am following this [link](https://docs.derivative.ca/Python_Drag/Drop_Experimental_Migration)
and then I used TouchDesigner 2020.44350 I wanna know why it gave me a error or is it my mistake? how to use this system ?

Firstly, I wanna it return a filetype when I droped a tox or jpg …