Describe the bug
PyTorch example suggests the use set_epoch function for DistributedSampler class before each epoch start. I could not find this function call in lightning's trainer module.

https://github.com/pytorch/examples/blob/master/imagenet/main.py
Line 232-234

As can be seen from the DistributedSampler class code (https://github.com/pytorch/pytorch/blob/master/torch/utils/data/distributed.py), the set_epoch function is required to set the seed for each iter function call.

Can you confirm if this function has been called on DistributedSampler (for training dataset) at some point in lightning's trainer module?