Solve a tuple error in Lua and unify Lua and Python tests

test/validation/items/py_func/py_func.py

@@ -16,8 +16,8 @@ def checkglobal(param):
     assert param=='test parameter'
     return 0
 
-def checkglobal2():
-    return tm.gd("py_func test parameter")
+def checkglobal2(index):
+    return tm.gd("data_to_be_returned")[index]
 
 def should_not_be_called(param):
     raise