Entension "SlicerVideoCameras" Loading problem

Dear Slicer’s user:
I download the Entension “SlicerVideoCameras”,
but after I download this, I couldn’t see the extension in my library,there might be some error here.Is there any error in the code or am I doing something wrong?
By the way,I’m using Slicer 4.10.2.
Import Entension SlicerVideoCameras
Thanks in advance!