input: 
  from typing import List
  
  def generate_unique_number(used_numbers: List[int]) -> int:
      """ Generate a unique 6-digit number that is not in the given list of used numbers.
      >>> generate_unique_number([100000, 100001, 100002])
      100003
      >>> generate_unique_number([])
      100000
      """
      while True:
          number = random.randint(100000, 999999)
          if number not in used_numbers:
              return number
  
output:     import random