How to close chrome browser's file upload window using selenium web driver with python code

My configuration : OS : Ubuntu 16.04 LTS, Development platform : Eclipse neon, Programe language : Python, Web driver : Selenium

I am creating a python script using selenium web driver (along with chrome driver)for send a mail with attachment via gmail

The script itself works as expected, but I unable to close the file upload window, after uploading a file

I am not find the element of file upload window (browser's window)

How to closed this window

So how can i close this attachment window.