Little typo

nexlibs/singleton.py

@@ -99,7 +99,7 @@ class Singleton(object, metaclass=MetaSingleton):
 
    def _getConstructionArgCountNotCountingSelf(cls):
       #return cls.__init__.__func__.__code__.co_argcount - 1
-      return six.get_function_code(cls.__init__).co_argument -1
+      return six.get_function_code(cls.__init__).co_argcount -1
    _getConstructionArgCountNotCountingSelf = classmethod(_getConstructionArgCountNotCountingSelf)
 
    def _forgetClassInstanceReferenceForTesting(cls):