input: Write a function to generate a random string of length 8.
  assert len(random_string_generator()) == 8
  assert isinstance(random_string_generator(), str)
  assert random_string_generator() != random_string_generator()
output: import random
  import string
  
  def random_string_generator():
      return ''.join(random.choices(string.ascii_letters + string.digits, k=8))