Modernize datasets: type hints and data splits handling (#1959)

SUMMARY:
Part of #1927. Addresses changes in `datasets` module ->
`src/llmcompressor/datasets/utils.py`


TEST PLAN:
- `make test`
- `make style`
- `pytest tests -m smoke`

---------

Signed-off-by: ojeda-e <[email protected]>
Co-authored-by: Brian Dellabetta <[email protected]>

Author: ojeda-e

src/llmcompressor/datasets/utils.py

@@ -9,7 +9,7 @@
 
 import multiprocessing
 import re
-from typing import Any, Callable, Dict, List, Optional
+from typing import Any, Callable
 
 import torch
 from datasets import Dataset
@@ -24,10 +24,10 @@
 
 def get_processed_dataset(
     dataset_args: DatasetArguments,
-    processor: Optional[Processor] = None,
+    processor: Processor | None = None,
     do_oneshot: bool = False,
     do_train: bool = True,
-) -> Optional[Dict[str, Dataset]]:
+) -> dict[str, Dataset] | None:
     """
     Loads datasets for each flow based on dataset_args, stores a Dataset for each
     enabled flow in datasets
@@ -50,17 +50,22 @@ def get_processed_dataset(
 
     def _get_split_name(inp_str):
         # strip out split name, for ex train[60%:] -> train
-        match = re.match(r"(\w*)\[.*\]", inp_str)
-        if match is not None:
-            return match.group(1)
+        split_name_match = re.match(r"(\w*)\[.*\]", inp_str)
+        if split_name_match is not None:
+            return split_name_match.group(1)
         return inp_str
 
-    if splits is None:
-        splits = {"all": None}
-    elif isinstance(splits, str):
-        splits = {_get_split_name(splits): splits}
-    elif isinstance(splits, List):
-        splits = {_get_split_name(s): s for s in splits}
+    match splits:
+        case None:
+            splits = {"all": None}
+        case str():
+            splits = {_get_split_name(splits): splits}
+        case list():
+            splits = {_get_split_name(s): s for s in splits}
+        case dict():
+            pass
+        case _:
+            raise ValueError(f"Invalid splits type: {type(splits)}")
 
     # default to custom dataset if dataset provided isn't a string
     registry_id = (
@@ -121,10 +126,10 @@ def get_calibration_dataloader(
 
 def format_calibration_data(
     tokenized_dataset: Dataset,
-    num_calibration_samples: Optional[int] = None,
+    num_calibration_samples: int | None = None,
     do_shuffle: bool = True,
     collate_fn: Callable = default_data_collator,
-) -> List[torch.Tensor]:
+) -> list[torch.Tensor]:
     """
     Creates a dataloader out of the calibration dataset split, trimming it to
     the desired number of calibration samples
@@ -172,10 +177,10 @@ def format_calibration_data(
 
 
 def make_dataset_splits(
-    tokenized_datasets: Dict[str, Any],
+    tokenized_datasets: dict[str, Any],
     do_oneshot: bool = True,
     do_train: bool = False,
-) -> Dict[str, Dataset]:
+) -> dict[str, Dataset]:
     """
     Restructures the datasets dictionary based on what tasks will be run
     train