Add a missing precondition to `DistributedSampler` docstring (#70104)
Summary:
Distributed sampler sets different indices for different processes. By doing this, it assumes that the data is the same across the board and in the same order. This may seem trivial, however, there are times that users don't guarantee the order items are gonna have, because they rely on something such as the order the filesystem lists a directory (which is not guaranteed and may vary on different computers), or the order a `set` is iterated.
I think it's better to make it clearer.
cc pietern mrshenli pritamdamania87 zhaojuanmao satgera rohan-varma gqchen aazzolini osalpekar jiayisuse SciPioneer H-Huang
Pull Request resolved: https://github.com/pytorch/pytorch/pull/70104
Reviewed By: bdhirsh
Differential Revision: D33569539
Pulled By: rohan-varma
fbshipit-source-id: 68ff028cb360cadaee8c441256c1b027a57c7089
