changed default override behavior

megatron/arguments.py

@@ -52,8 +52,11 @@ def parse_args(extra_args_provider=None, defaults={},
         # For default to be valid, it should not be provided in the
         # arguments that are passed to the program. We check this by
         # ensuring the arg is set to None.
-        assert getattr(args, key) is None, \
-            'defaults can only be overwritten for args with None values.'
+        if getattr(args, key) is not None:
+            print('WARNING: overriding default arguments for {key}:{v} with \
+                    {key}:{v2}'.format(key=key, v=defaults[key],
+                                       v2=getattr(args, key))
+        else:
             setattr(args, key, defaults[key])
 
     # Check required arguments.