input: Write a function to remove duplicates from a list.
  assert remove_duplicates([4, 5, 1, 9, 5, 4, 3]) == [1, 3, 4, 5, 9]
  assert remove_duplicates([10, 20, 20, 10, 30]) == [10, 20, 30]
  assert remove_duplicates([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) == [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
output: def remove_duplicates(lst):
      return sorted(set(lst))