docs: def duplicates(coll):
      """Return the duplicated items in the given collection
  
      :param coll: a collection
      :returns: a list of the duplicated items in the collection
  
      >>> duplicates([1, 1, 2, 3, 3, 4, 1, 1])
      [1, 3]
  
      """
      return list(set(x for x in coll if coll.count(x) > 1))