Invalid usage of torch.no_grad Context manager
🐛 Bug

Using no_grad context manager in  the following line 
  
    
      pytorch-lightning/pytorch_lightning/utilities/distributed.py
    
    
         Line 210
      in
      127454a
    
  
  
    

        
          
           with torch.no_grad: 
        
    
  


is incorrect as the context manager is callable. Parentheses are missing.
The line should be: with torch.no_grad():
Please reproduce using the BoringModel and post here

https://colab.research.google.com/drive/1snyzXx4G6QCatbs6bN2GCsTFIMdItvmm?usp=sharing
To Reproduce

Expected behavior

No AttributeError enter
gathered_loss == loss in BoringModel

Environment
Note: Bugs with code are solved faster ! Colab Notebook should be made public !


IDE: Please, use our python bug_report_model.py template.


Colab Notebook: Please copy and paste the output from our environment collection script (or fill out the checklist below manually).


You can get the script and run it with:
wget https://raw.githubusercontent.com/PyTorchLightning/pytorch-lightning/master/tests/collect_env_details.py
# For security purposes, please check the contents of collect_env_details.py before running it.
python collect_env_details.py


CUDA:

GPU:

Tesla P100-PCIE-16GB


available:         True
version:           10.1


Packages:

numpy:             1.18.5
pyTorch_debug:     True
pyTorch_version:   1.7.0+cu101
pytorch-lightning: 1.1.0
tqdm:              4.41.1


System:

OS:                Linux
architecture:

64bit



processor:         x86_64
python:            3.6.9
version:           #1 SMP Thu Jul 23 08:00:38 PDT 2020



Additional context

Training using "ddp" accelerator with arbitrary number of gpus.