singleton-decorator declared in setup.py but not used?

[kdzhao]

Not exactly a bug nor feature per se, but in the setup file it says requires "singleton-decorator", which I assume it is this one:
https://github.com/Kemaweyan/singleton_decorator
But after some search in this code base and I didn't see where this package is being used. Or maybe my understanding is wrong?

Thanks

[kdzhao]

Any comments? Thanks!