Allow refresh() to take args (#95)

`refresh()` can be called with args, so accept arbitrary args for the fake implementation.

This was an issue internally, where refresh appears to be called with args.

tests/test_operations.py

@@ -64,7 +64,7 @@ def test_end_to_end(self):
 
         # Create the operation with the `initial_pb` but when it asks for an update
         # return the `final_pb`.
-        def refresh():
+        def refresh(*_, **__):
             return final_pb
 
         # This is the base Operation class
@@ -133,7 +133,7 @@ def make_metadata(completed_steps):
         ops = gen_operations()
         initial_pb = next(ops)
 
-        def refresh():
+        def refresh(*_, **__):
             """get the next status on each refresh"""
             return next(ops)