Exercise 1

def find_dups(list):

""" (list) -> set
""" 
 elem_set = set()
 dups_set = set()
 for entry in list:
     len_initial = len(elem_set)
     elem_set.add(entry)
     len_after = len(elem_set)
     if len_initial == len_after:
         dups_set.add(entry)
return(dups_set)