input: from typing import List
  
  def generate_unique_number(existing_numbers: List[int]) -> int:
      """ Generate a unique 6-digit number that is not in the given list of existing numbers.
      >>> generate_unique_number([12345, 67890])
      10000
      >>> generate_unique_number([10000, 10001, 10002])
      10003
      """
      all_6_digit_numbers = set(range(10000, 100000))
      available_numbers = all_6_digit_numbers - set(existing_numbers)
      return random.choice(list(available_numbers))
output:     import random
      all_6_digit_numbers = set(range(100000, 1000000))
      available_numbers = all_6_digit_numbers - set(existing_numbers)
      return random.choice(list(available_numbers))