question: Disabling find_unused_parameters
context: When trying to disable find_unused_parameters in the trainer by doing the following,
  strategy=DDPStrategy(find_unused_parameters=False)
  Am being thrown an import error for from pytorch_lightning.strategies import DDPStrategy
  Error:
  No module named 'pytorch_lightning.strategies'
answer: pytorch_lightning.strategies will be available in v1.6 release and is only available in master at the moment.
  For now, you can use:
  from pytorch_lightning.plugins import DDPPlugin
  
  trainer = pl.Trainer(
      ...,
      strategy=DDPPlugin(find_unused_parameters=False),
  )
  
  See the stable version of docs (not latest) here: https://pytorch-lightning.readthedocs.io/en/stable/guides/speed.html?highlight=find_unused_parameters#when-using-ddp-plugins-set-find-unused-parameters-false