修复dpo报错

backend/app/engines/text_engine.py

@@ -317,7 +317,7 @@ class TextEngine(BaseEngine):
                 ref_model=ref_model,
                 args=DPOConfig(**base_trainer_kwargs),
                 train_dataset=dataset,
-                processing_class=self._tokenizer,
+                tokenizer=self._tokenizer,
             )
         elif task_type == "ppo":
             import torch