input: Write a function to generate a random number between 0 and 9. Return the generated number.
  assert generate_random_number() in range(10)
  assert generate_random_number() in range(10)
  assert generate_random_number() in range(10)
  assert generate_random_number() in range(10)
  assert generate_random_number() in range(10)
output: import random
  
  def generate_random_number():
      return random.randint(0, 9)