input: def deleteDuplicates(numbers: List[int]) -> List[int]:
      """ Delete all duplicates in a given list of numbers.
      >>> deleteDuplicates([1, 2, 2, 3, 4, 4, 5])
      [1, 2, 3, 4, 5]
      >>> deleteDuplicates([10, 20, 30, 20, 40, 10, 50])
      [10, 20, 30, 40, 50]
      """
output:     seen = set()
      result = []
      for num in numbers:
          if num not in seen:
              seen.add(num)
              result.append(num)
      return result