input: Write a function to generate a random 6-digit number in Python. The function should return the generated number.
  
  assert generate_random_number()==123456
  assert generate_random_number()==987654
  assert generate_random_number()==123123
  
  Note: The actual output of the function may vary each time it is run, but the assert statements are provided to illustrate the expected range of the output.
output: import random
  
  def generate_random_number():
      return random.randint(100000, 999999)