how to find edge from data in excel : If I have this data :
      
      'data for id_books that user_id borrowed
        user_id        id_book     book
        1                55        physic           
        2                55        physic
        2                55        physic
        3                55        physic
        4                55        physic

this is the output is show me the users that borrowed the same book from library :
   
       '                      
        nodes(user_id):       edges(relation between user_id)
                               source,target
          1                    1,2
          2                    1,3
          3                    1,4 
          4                    2,3
                               2,4
                               2,3
                               2,4
'
                               
 is that correct to show me 1,2 just once?