input: from typing import List
  
  def remove_duplicates(my_list: List[int]) -> List[int]:
      """ Remove duplicates from a given list and return the unique elements.
      >>> remove_duplicates([1, 2, 3, 4, 3, 2, 1])
      [1, 2, 3, 4]
      """
output:     seen = set()
      unique_list = []
      for item in my_list:
          if item not in seen:
              seen.add(item)
              unique_list.append(item)
      return unique_list