None
{"headers":{"Activity":["user_id","session_id","activity_date","activity_type"]},"rows":{"Activity":[[1,1,"2019-07-20","open_session"],[1,1,"2019-07-20","scroll_down"],[1,1,"2019-07-20","end_session"],[2,4,"2019-07-20","open_session"],[2,4,"2019-07-21","send_message"],[2,4,"2019-07-21","end_session"],[3,2,"2019-07-21","open_session"],[3,2,"2019-07-21","send_message"],[3,2,"2019-07-21","end_session"],[3,5,"2019-07-21","open_session"],[3,5,"2019-07-21","scroll_down"],[3,5,"2019-07-21","end_session"],[4,3,"2019-06-25","open_session"],[4,3,"2019-06-25","end_session"]]}}