input: Write a function to generate a random number between 0 and 9. The function should take no input and return the generated random number.
  assert generate_random_num() in range(10)
  assert generate_random_num() in range(10)
  assert generate_random_num() in range(10)
  assert generate_random_num() in range(10)
  assert generate_random_num() in range(10)
output: import random
  
  def generate_random_num():
      return random.randint(0, 9)