fix missing self. (#61)

Co-authored-by: 许文卿 <xuwenqing@XWQ.local>

modelscope/trainers/cv/image_classifition_trainer.py

@@ -423,7 +423,7 @@ class ImageClassifitionTrainer(BaseTrainer):
             classname_path = osp.join(data_root, 'classname.txt')
             classes = classname_path if osp.exists(classname_path) else None
         else:
-            classes = cfg.dataset.classes
+            classes = self.cfg.dataset.classes
         dataset = MmDataset(
             self.eval_dataset,
             pipeline=preprocess_transform(self.cfg.preprocessor.val),