input: Write a function to generate a random integer within the range [0, 10). The function should import the `random` module and use its `randint` method to generate the random number. If the range is invalid, the function should return None.
  
  def generate_random_number_in_range():
      import random
      return random.randint(0, 9)
  
  assert generate_random_number_in_range() is not None
  # Since the function generates a random number, multiple calls may be necessary to confirm functionality.
output: def generate_random_number_in_range():
      import random
      return random.randint(0, 9)