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