code: def remove_duplicates(items):
      
      if items is None:
          return items
  
      new_list = []
      for item in items:
          if item not in new_list:
              new_list.append(item)
      return new_list
docs: Returns a list without duplicates, keeping elements order
  
      :param items: A list of items
      :return: The list without duplicates, in the same order