Getting error when ran the example files.

./ale_python_test2.py space_invaders.bin
A.L.E: Arcade Learning Environment (version 0.5.1)
[Powered by Stella]
Use -help for help screen.
Warning: couldn't load settings file: ./ale.cfg
Traceback (most recent call last):
File "./ale_python_test2.py", line 19, in
ale.set("random_seed",123)
AttributeError: 'ALEInterface' object has no attribute 'set'