modify style & little change

Former-commit-id: c988477d14dc656450d5fec31895781b7f9f7dce

src/llamafactory/data/collator.py

@@ -99,6 +99,9 @@ class MultiModalDataCollatorForSeq2Seq(DataCollatorForSeq2Seq):
 
         features: Dict[str, "torch.Tensor"] = super().__call__(features)
         features.update(mm_inputs)
+        if features.get("pixel_values") is not None and isinstance(features["pixel_values"], list):
+            features = features.data
+
         return features