Python 3

Take advantage of the fact that the range of the integers in the list is fixed (0 to m, where m is the largest ID you can find in the linked list). Use a boolean array seen of length m+1 to indicate if elements in the array have been seen before. Then determine if there are duplicates by performing a single pass through the unsorted list. Hint: while traversing the list, seen[item] = True if integer item has been seen before in the search. How would i write the method?

I'm passing a list and checking for duplicates and returning true or false if duplicates have been seen. I'm not getting it.