fix: raise warning when using Global.class_num

ppcls/engine/engine.py

@@ -113,6 +113,14 @@ class Engine(object):
             }
             paddle.fluid.set_flags(AMP_RELATED_FLAGS_SETTING)
 
+        if "class_num" in config["Global"]:
+            global_class_num = config["Global"]["class_num"]
+            if "class_num" not in config["Arch"]:
+                config["Arch"]["class_num"] = global_class_num
+                msg = f"The Global.class_num will be deprecated. Please use Arch.class_num instead. Arch.class_num has been set to {global_class_num}."
+            else:
+                msg = "The Global.class_num will be deprecated. Please use Arch.class_num instead. The Global.class_num has been ignored."
+            logger.warning(msg)
         #TODO(gaotingquan): support rec
         class_num = config["Arch"].get("class_num", None)
         self.config["DataLoader"].update({"class_num": class_num})