Can't get attribute '_gpus_arg_default'
🐛 Bug
when I use the code
model = model.load_from_checkpoint(ckpt_path)
It pops out a problem: Can't get attribute '_gpus_arg_default' on <module 'pytorch_lightning.utilities.argparse' from '/opt/conda/envs/lasaft/lib/python3.8/site-packages/pytorch_lightning/utilities/argparse.py'>
To Reproduce
Very hard to describe the reproduction, because I could not load model.
Expected behavior
Succeed in loading the model
Environment

PyTorch Version (e.g., 1.0):1.7.1
OS (e.g., Linux): Ubuntu 18.04
How you installed PyTorch (conda, pip, source): conda
Build command you used (if compiling from source):
Python version: 3.8.5
CUDA/cuDNN version: 10.2
GPU models and configuration: V100
Any other relevant information: PL version is 1.3.0rc1