FLATTEN is not working

[Mix Nin]

I have a file with below data

xxxxx   11,22,33        44,55,66        77,88,99

I wrote below PIG  script

X= LOAD '/user/lnindrakrishna/tmp/ExpTag.txt' AS (id :chararray,qc
:chararray ,qt :chararray ,qe :chararray  );

Y = Foreach X generate id, STRSPLIT(qc,',') AS split_qc  , STRSPLIT(qt,',')
AS  split_qt, STRSPLIT(qe,',') AS split_qe;;

Z = foreach Y generate id, FLATTEN(TOBAG(split_qc));

I expected output as follows:

xxxxx 11
xxxxx 22
xxxxx 33

But the above script is producing output as follows

(xxxxx,11,22,33)

FLATTEN is not actually flattening the bag of tuple. Any inputs here?

- Thanks