title: how to create set of values, after group function in Pig (Hadoop)
body: <p>Lets say I have set of values in file.txt <br>
      a,b,c<br>
      a,b,d<br>
      k,l,m<br>
      k,l,n<br>
      k,l,o<br>
  <br>
  And my code is:<br>
      file = LOAD 'file.txt' using PigStorage(',');<br>
      events = foreach file generate session_id, user_id, code, type;<br>
      gr = group events by (session_id, user_id);<br>
  <br>
  and I have set of value:<br></p>
  
  <p>((a,b),{(a,b,c),(a,b,d)})<br>
  ((k,l),{(k,l,m),(k,l,n),(k,l,o)})<br></p>
  
  <p>And I'd like to have:
  (a,b,(c,d))<br>
  (k,l,(m,n,o))<br></p>
  
  <p>Have you got any idea how to do it?</p>
  
  <p>Regards
  Pawel</p>