input: Write a function to generate a random 6-digit number in Python and return the generated number.
  assert random_6_digit_number()==123456
  assert random_6_digit_number()==987654
  assert random_6_digit_number()==112233
  assert random_6_digit_number()==998877
  assert random_6_digit_number()==246810
  assert random_6_digit_number()==135790
output: import random
  
  def random_6_digit_number():
      return random.randint(100000, 999999)