input: 
  def deleteDuplicates(numbers: list) -> list:
      """ Deletes all duplicates in a given list of numbers and returns the list without duplicates.
      >>> deleteDuplicates([1, 2, 3, 2, 1])
      [1, 2, 3]
      >>> deleteDuplicates([4, 5, 6, 5, 4, 7])
      [4, 5, 6, 7]
      """
      final_list = []
      for num in numbers:
          if num not in final_list:
              final_list.append(num)
      return final_list
  
output:     final_list = []
      for num in numbers:
          if num not in final_list:
              final_list.append(num)
      return final_list