order_by checks if its first argument is an instance of types.FunctionType. This makes it impossible to use it with general callables like methods, instances with __call__, operator.itemgetter(-1) etc. It should therefore changed to check for if callable(args[0]).
order_bychecks if its first argument is an instance oftypes.FunctionType. This makes it impossible to use it with general callables like methods, instances with__call__,operator.itemgetter(-1)etc. It should therefore changed to check forif callable(args[0]).