'DistributedWorker' object has no attribute 'world_size'

There are some other errors at first, and I copied the lost files the error shows from the https://github.com/hwang595/ps_pytorch,  now when I simply run run_pytorch_single.sh here, it shows 'DistributedWorker' object has no attribute 'world_size', and I checked distributed_worker.py, it doesn't have that attribute indeed, don't know how to deal with it.