code: def find_duplicates(l: list) -> set:
      
      return set([x for x in l if l.count(x) > 1])
docs: Return the duplicates in a list.
  
      The function relies on
      https://stackoverflow.com/questions/9835762/find-and-list-duplicates-in-a-list .
      Parameters
      ----------
      l : list
          Name
  
      Returns
      -------
      set
          Duplicated values
  
      >>> find_duplicates([1,2,3])
      set()
      >>> find_duplicates([1,2,1])
      {1}