Group by, without having key in old relation

[Lai Will]

Hi there

Let's say I have

DUMP A
(user1, date1, {(item1), (item2)}, {(skill1), (skill2)})
(user1, date2, {(item3), (item4), (item5)}, {(skill1), (skill3)})
(user2, date2, {(item2), (item5)}, {(skill4})

When I do 

B = GROUP A by user

I get

user1 {(user1, date1, {(item1), (item2)}, {(skill1), (skill2)}), (user1, date2, 
{(item3), (item4), (item5)}, {(skill1), (skill3)}) }
user2 {(user2, date2, {(item2), (item5)}, {(skill4})}

this is actually fine, but better would be to have the previous relation 
without the group by key contained:

user1 {(date1, {(item1), (item2)} , {(skill1), (skill2)}), (date2, {(item3), 
(item4), (item5)}, {(skill1), (skill3)})}
user2 {(date2, {(item2), (item5)} , {(skill4})}

what's the easiest way to achieve this?

Best,
Will