Slice splits support for datasets.load_from_disk

[mhorlacher]

Feature request

Support for slice splits in datasets.load_from_disk, similar to how it's already supported for datasets.load_dataset.

Motivation

Slice splits are convienient in a numer of cases - adding support to datasets.load_from_disk would make working with local datasets easier and homogenize the APIs of load_from_disk and load_dataset.

Your contribution

Sure, if the devs think the feature request is sensible.