{
     "user1":["l1","l2","l3","l4","l5"]
     "user2":["l2","l3",l4","l7"]
     "user3":["l7,"l5"]
}

{
      "l1":[user1]
      "l2":[user1,user2]
      "l3":[user1,user2]
      "l4":[user1,user2]
      "l5":[user1,user3]
      "l7":[user2,user3]
}