input: 
  def generate_number() -> int:
      """
      Generate a unique 6-digit number.
      >>> generate_number()
      12345
      >>> generate_number()
      67890
      >>> generate_number()
      54321
      """
      import random
      return random.randint(100000, 999999)
  
output:     import random
      return random.randint(100000, 999999)