Remove unused method and variable in base.py

base.py was migrated and simplified by
 commit: 45da2a78dc9d560b021ae3fa90d9b7e45b6c9b51
But there are some unused codes in it. This commit just removes them.

Change-Id: Ie16fdf75b69006cf48ad9b2649c4bf3659901b80
Merge "Remove unused method and variable in base.py"