questions for the patch 'Enable pl/python to return records based on multiple OUT params' during reviewing

I created a function for testing the patch, but when i run following command, the function always raise an exception

select test_in_params('first');
ERROR:  plpython: function "test_in_params" failed
DETAIL:  exceptions.NameError: global name 'first' is not defined

here is the script of fucntion
create or replace function test_in_params(first text)
   returns text
as $$
return first + 'first'
$$LANGUAGE plpythonu;

Anyone help me   Thanks