input: Write a python function to remove duplicates from a list.
  assert remove_duplicates([1, 2, 2, 4, 5]) == [1, 2, 4, 5]
  assert remove_duplicates([1, 1, 1, 2, 2, 3, 4]) == [1, 2, 3, 4]
  assert remove_duplicates([5, 4, 3, 2, 1, 1, 1]) == [5, 4, 3, 2, 1]
  assert remove_duplicates([]) == []
output: def remove_duplicates(lst):
      return list(dict.fromkeys(lst))