input: Write a function to remove all duplicate elements from a given list of integers. The function should return a new list that contains only the unique elements in their original order of appearance. If the input list is empty, the function should return an empty list.
  
  def remove_duplicates(list_of_integers):
      if not list_of_integers:
          return []
      final_list = []
      for num in list_of_integers:
          if num not in final_list:
              final_list.append(num)
      return final_list
  
  assert remove_duplicates([1, 2, 3, 2, 4, 5, 6, 3]) == [1, 2, 3, 4, 5, 6]
  assert remove_duplicates([1, 1, 1, 1]) == [1]
  assert remove_duplicates([1, 2, 3, 4, 5]) == [1, 2, 3, 4, 5]
  assert remove_duplicates([]) == []
  assert remove_duplicates([10, 20, 30, 20, 10, 40]) == [10, 20, 30, 40]
output: def remove_duplicates(list_of_integers):
      if not list_of_integers:
          return []
      final_list = []
      for num in list_of_integers:
          if num not in final_list:
              final_list.append(num)
      return final_list