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