input: Write a function to generate a random 6-digits number in Python. The function should return the generated number.
  assert generate_six_digit_number()==100000
  assert generate_six_digit_number()==999999
  import random
  
  def generate_six_digit_number():
      return random.randint(100000, 999999)
output: import random
  
  def generate_six_digit_number():
      return random.randint(100000, 999999)