fix: use hasattr() to check if collate_fn is in dataloader

fix bug caused by PR #1596

ppcls/engine/engine.py

@@ -161,7 +161,7 @@ class Engine(object):
             if metric_config is not None:
                 metric_config = metric_config.get("Train")
                 if metric_config is not None:
-                    if self.train_dataloader.collate_fn:
+                    if hasattr(self.train_dataloader, "collate_fn"):
                         for m_idx, m in enumerate(metric_config):
                             if "TopkAcc" in m:
                                 msg = f"'TopkAcc' metric can not be used when setting 'batch_transform_ops' in config. The 'TopkAcc' metric has been removed."