simplify code

Former-commit-id: d3731754ab7c28ae81f60784e0e4213f279d93fe

src/llmtuner/dsets/utils.py

@@ -0,0 +1,16 @@
+from typing import Dict
+from datasets import Dataset
+
+
+def split_dataset(
+    dataset: Dataset, dev_ratio: float, do_train: bool
+) -> Dict[str, Dataset]:
+    # Split the dataset
+    if do_train:
+        if dev_ratio > 1e-6:
+            dataset = dataset.train_test_split(test_size=dev_ratio)
+            return {"train_dataset": dataset["train"], "eval_dataset": dataset["test"]}
+        else:
+            return {"train_dataset": dataset}
+    else: # do_eval or do_predict
+        return {"eval_dataset": dataset}