allow non-packing pretraining

Former-commit-id: 3fee5cc5a3db9ce874ad90f2500ec092d904bd4e

src/llmtuner/extras/ploting.py

@@ -1,7 +1,7 @@
 import json
 import math
 import os
-from typing import List, Optional
+from typing import List
 
 from transformers.trainer import TRAINER_STATE_NAME
 
@@ -30,7 +30,7 @@ def smooth(scalars: List[float]) -> List[float]:
     return smoothed
 
 
-def plot_loss(save_dictionary: os.PathLike, keys: Optional[List[str]] = ["loss"]) -> None:
+def plot_loss(save_dictionary: os.PathLike, keys: List[str] = ["loss"]) -> None:
     with open(os.path.join(save_dictionary, TRAINER_STATE_NAME), "r", encoding="utf-8") as f:
         data = json.load(f)