input: from typing import List
  
  
  def find_duplicate_numbers(numbers: List[int]) -> List[int]:
      """
      Given a list of integers, find and return a list of all the numbers that appear more than once in the input list.
      Each duplicate number should only appear once in the result list.
  
      >>> find_duplicate_numbers([1, 2, 3, 2, 4, 3, 5])
      [2, 3]
      >>> find_duplicate_numbers([1, 1, 1, 2, 2, 3, 4, 4, 5])
      [1, 2, 4]
      """
      seen = set()
      duplicates = set()
      for num in numbers:
          if num in seen:
              duplicates.add(num)
          else:
              seen.add(num)
      return list(duplicates)
output:     seen = set()
      duplicates = set()
      for num in numbers:
          if num in seen:
              duplicates.add(num)
          else:
              seen.add(num)
      return list(duplicates)