load_dataset splits typing (#7587)

* typing

* again

Author: lhoestq

src/datasets/builder.py

@@ -1066,7 +1066,7 @@ def _make_split_generators_kwargs(self, prepare_split_kwargs):
 
     def as_dataset(
         self,
-        split: Optional[Split] = None,
+        split: Optional[Union[str, Split, list[str], list[Split]]] = None,
         run_post_process=True,
         verification_mode: Optional[Union[VerificationMode, str]] = None,
         in_memory=False,

src/datasets/load.py

@@ -1840,7 +1840,7 @@ def load_dataset(
     name: Optional[str] = None,
     data_dir: Optional[str] = None,
     data_files: Optional[Union[str, Sequence[str], Mapping[str, Union[str, Sequence[str]]]]] = None,
-    split: Optional[Union[str, Split]] = None,
+    split: Optional[Union[str, Split, list[str], list[Split]]] = None,
     cache_dir: Optional[str] = None,
     features: Optional[Features] = None,
     download_config: Optional[DownloadConfig] = None,