input: Write a python function to filter out duplicate values from a list.
  assert filter_list([14, 15, 16, 16, 19, 20, 20, 21, 19]) == [14, 15, 16, 19, 20, 21]
  assert filter_list([1, 2, 2, 3, 4, 4, 5]) == [1, 2, 3, 4, 5]
  assert filter_list([7, 8, 8, 9, 10, 10, 11]) == [7, 8, 9, 10, 11]
output: def filter_list(lst):
      return list(dict.fromkeys(lst))