Dropping one tuple from the bag purposefully

[felix gao]

Ok, this might sound little weird.

my schema is f1, f2, f3 ,f4, f5, f6
when group by f1, f2, f3. I need to drop exactly one tuple when I have more
than one tuples by grouping f1,f2,f3. Also the values of the tuples in each
group could occur more than once.

Is there a way to do it in pig?

Thanks,

Felix