Try to change API

python/paddle/fluid/io.py

@@ -27,10 +27,14 @@ __all__ = [
     'get_inference_program', 'save_checkpoint', 'load_checkpoint',
     'clean_checkpoint', 'load_persist_vars_without_grad',
     'load_lookup_table_vars', 'save_persist_vars_without_grad',
-    'get_latest_checkpoint_serial'
+    'get_latest_checkpoint_serial', 'foo'
 ]
 
 
+def foo():
+    pass
+
+
 def is_parameter(var):
     """
     Check whether the given variable is an instance of Parameter.