pip install pytorch-lightning["extra"] doesn't install FairScale
🐛 Bug
The documentation [0] states that to enable sharded training one needs to install the extras packages with pip install pytorch-lightning["extra"], in my case only following the second option pip install https://github.com/PyTorchLightning/fairscale/archive/pl_1.1.0.zip actually installed fairscale.
[0] https://pytorch-lightning.readthedocs.io/en/stable/multi_gpu.html#model-parallelism-beta
To Reproduce
pip install pytorch-lightning["extra"]
Expected behavior
Fairscale gets installed.
Environment

PyTorch Version 1.7.0
OS: Linux
How you installed PyTorch: pip
Python version: 3.6.9
CUDA/cuDNN version: 10.2
GPU models and configuration: 4x TITAN X