[DataLoader] `__getitems__` added to description of Dataset API and better supported within `Subset` (#100375)
DataLoader supports batched loading from Mapped Datasets.
This is the fetcher's implementation of auto-detection of batch loading support.
torch.utils.data._utils.fetch._MapDatasetFetcher
```
class _MapDatasetFetcher(_BaseDatasetFetcher):
def fetch(self, possibly_batched_index):
if self.auto_collation:
if hasattr(self.dataset, "__getitems__") and self.dataset.__getitems__:
data = self.dataset.__getitems__(possibly_batched_index)
else:
data = [self.dataset[idx] for idx in possibly_batched_index]
```
Description of Dataset API now shows this feature.
Additionally, Subset dataset now supports `__getitems__` if parent dataset supports it.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/100375
Approved by: https://github.com/ejguan, https://github.com/NivekT
