input: Write a function to remove duplicates from a given list and return the list with unique elements in the same order they first appear. Repeat the process for different lists and verify the correctness of the function.
  
  def remove_duplicates(my_list):
      return list(dict.fromkeys(my_list))
  
  assert remove_duplicates([1, 2, 3, 4, 3, 2, 1]) == [1, 2, 3, 4]
  assert remove_duplicates([5, 6, 7, 6, 7, 8]) == [5, 6, 7, 8]
  assert remove_duplicates([]) == []
  assert remove_duplicates([9, 9, 10, 10, 9, 11]) == [9, 10, 11]
  assert remove_duplicates([1, 2, 3, 2, 1, 2, 3, 4]) == [1, 2, 3, 4] 
  
output: def remove_duplicates(my_list):
      seen = set()
      result = []
      for item in my_list:
          if item not in seen:
              seen.add(item)
              result.append(item)
      return result