baffling error attention--“ Unused import statement”

Hi,there!
when i working with Pycharm, Eventhough I have used the the import thing,the IDE still tells me it's "Unused import statement"? [you can see details in the picture]
Is there any error in my code? Or it's a bug?
PS: python version is 3.7 Pycharm version is 2017.2.3

the code:

import random
import urllib.parse
import urllib.request

data = urllib.parse.urlencode("http://1212.ip138.com/ic.asp")
res = urllib.request.urlopen("http://1212.ip138.com/ic.asp").read().strip("\n")