input: 
  from typing import List
  import random
  
  def generate_unique_6_digit_number() -> int:
      """ Generate a unique 6-digit number
      >>> generate_unique_6_digit_number()
      10000
      >>> generate_unique_6_digit_number()
      99999
      """
      return random.randint(100000, 999999)
  
output:     while True:
          number = random.randint(100000, 999999)
          if len(set(str(number))) == 6:
              return number