input: Write a python function to generate a random password of 8 characters.
  assert len(random_password()) == 8
  assert isinstance(random_password(), str)
  assert all(c in (string.ascii_lowercase + string.digits + string.ascii_uppercase) for c in random_password())
output: import random
  import string
  
  def random_password():
      characters = string.ascii_letters + string.digits
      return ''.join(random.choice(characters) for _ in range(8))